Both computers are actually based on a reference design from Motorola, the Microchroma 68, featuring a version of the MEK6800D2 MikBug monitor called TVbug. This was essentially what is in the coco (and dragon) computer. Tandy used this base design to create a Videotex terminal for farmers called the AgVision, and if you google for that you will see its actually a blue coco, it even has facilities for what later became its cartridge connector. What I want to say is that Tandy cannot claim ownership of the CoCo's architecture as it not theirs, its Motorola's. They simply took the Microchroma 68 design put it in a somewhat nice case and replaced TVbug with a BASIC written by Microsoft.
If you have a T1 VDG in the Coco, try this: POKE 359,57:POKE 65314,80. If the border turns green, and SHIFT-0 toggles between true upper and lowercase letters (as you type them), then you truly do have a T1. There is a version of OS-9 Level 1 that supports that fully, as well as numerous terminal programs, etc. Also, there is a trick to convert BASIC programs between them without retyping them (or using special utilities): Save them in ASCII format (for example CSAVE "PROGRAM",A). It is slower, but it doesn't tokenize. Also, one thing that is completely different is the disk drive ROM and disk drive formats; the Coco's use granules (9 sector blocks) while the Dragon uses actual sectors, and also supports >35 tracks. (The disk controllers on both can handle up to 80 tracks and double sided just fine; it's the Disk Extended BASIC vs. Dragon DOS ROM's that are completely different). Also, the CocoSDC also emulates hard drives as well (the Coco 3 with NitrOS-9 EOU is based on that).
In 1983 I designed a children's computer using that same Motorola chipset, so it was pretty similar to the CoCo. But there were many differences (serial keyboard, network, Logo in ROM, no cartridge, different sound). Not long after that a bunch of CoCo clones were launched in Brazil (Prologica CP400, Codimex CD6809, Dynacom MX-1600, Engetecnica VC50, NovoTempo/LZ Color64). That made people think my machine had been a clone as well.
I seem to remember a blurb about the Dragon being designed with aid from Motorola and based on their reference design, but as you said the details are a bit too similar. I'd guess a believable scenario would be someone just handing them the schematic as a reference to the problem already being solved before. The most telling part is that in the MC6847 datasheets they used a dedicated chip for the colour circuits, but here they've both got a dedicated circuit instead. I would think Motorola would have sold them on that chip instead of all those components.
It seems feasible that Motorola might have directed the design for increased compatability with the existing platform. When Mettoy set out to create a computer it doesn't seem like they had a lot of requirements except "we need it yesterday". And Motorola had worked together with Tandy to create the Coco.
I didn't play a lot of games on my Coco. However, I did a lot of hardware development. I built several peripherals for it including a universal EPROM programmer, a text to speech card, and a 6809 In-Circuit emulator that worked by allowing the Coc's 6809 to take over the target system's bus. I also build a data logging card that used a small fast ADC that had a two-wire multi-device interface that I had to bit-bang. I did many other projects as well. I miss the days of direct access to hardware! As for software, my favorite programs were the assembler cart and the terminal program that allowed me to dial into my favorite BBS. Remember those?
Looks like they both came from the same reference design, so they are brothers, so to speak. The chipset and the Microsoft Basic emulator put restrictions on the way the system is designed, but Dragon64 design team did take advantage of what little leeway their was and distanced themselves from the Tandy machines. Legal fights based on forced commonality would not have much teeth in court. Thanks for the comparison, good stuff! Cheers,
Excellent Work as usual. Owning a Dragon 32 and CoCo2 this video was particularly interesting for me. I like the Dragon more myself as well. Just because most people here don't know it exists. Awaiting a CoCoSDC, Glad to know it has your seal of approval.
Thank you! Now I'm curious about the Tano Dragon and what's different about it. Up until a few years ago you could still buy them new old stock for about $100 I think, but they've been out for a while.
Very thorough and unique approach as usually. I'm the owner of a cpc6128 and one of the things I would like is someone to make a step by step tutorial on how to make the simplest rom expansion, just one rom using one eprom / eeprom. As few components as possible. There are many products that do this but diy is what I'm looking for. The already available designs, include 4 or 6 roms and really, you need to solder a very large number of cables making them unattractive and cumbersome. I wish you consider this for a future tutorial.
i wanna know how/if its possible.. to convert it from the multiple DRAM chips to a single SRAM..or have a rom expansion that takes over from main ram from the get go.. (im having trouble sourcing 4164s atm)
The 6809 was an amazing CPU for its time, far superior to the 6502 I would say. 6809 assembly language is actually fun to program. Apparently the price was a stumbling block and so it was rarely used. A shame really.
It has more accumulators, more (16-bit) index registers, more (16-bit) stack pointers, more addressing modes, hardware multiply, and an 8-bit register that allows you to position the Direct Page anywhere in memory.
@@joelavcoco Indeed. It's a shame the 6809 didn't see more use. Imagine how much better the software would have been back in the day. They did remarkable things with the 6502, but at the end of the day you can't get blood from a stone.
My favourite game for the Dragon32 was Manic Miner, which I used to play constantly. I've recently managed to find Dos version of this which I am now playing and once again i'm hooked
Both of these don't look like much but they actually feature the best (and most expensive) 8-bit CPU ever. The 6809 is like the grand daddy of the 6502 and very much prepared to run a real multi-tasking operating system as we know it today.
@@lawrencemanning As is probably clear to anybody who's written just a few thousand lines of assembler for each, the 6502 is remarkably well designed, with a number of design choices that were clear improvements over its inspiration the 6800 (not the 6809, which came years later) even when you're not taking cost into account. Among other things these include removing some of the most annoying behaviours of the 6800 (setting flags on stores, not being able to push the index register), being little-endian to save a cycle on any instruction involving a 16-bit address calculation, and being able to do indirect memory access through an address in any zero page location, rather than just through a single index register. Though the cost considerations seem to have precluded making a CPU that was better in every respect than the 6800, the 6502 designers did produce a CPU that was faster and had more powerful addressing modes, as well as being well under half the price.
The greatest thing about the 6809/6502 was the PCR (Program Counter Relative) data instructions, which meant that it was possible to make a program completely relocatable in memory. I used that feature in a machine-code program which was designed to allow a BASIC program to print the entire IBM extended ASCII character set on the "high resolution" display on the COCO. The data for the characters took up more space than the program did, yet the program had advanced features such as allowing the BASIC program to redefine characters without having to know where to POKE the character definitions in memory; print characters in reverse video; reposition the cursor; clear the screen and home the cursor and so on.
I had both the VIC20 and CC3. I can say today I am a firmware and hardware engineer... Those days as a kid typing in games from a magazine got me intreated in programming and engineering.. Loved those days!!!
Great video! Thank you for sharing! The Tandy Radio Shack Color Computer 2 is what I started with. Though the model I had used the standard 6847 not the T1 version. As far as the Dragon64 goes the serial chip is a MOS 6551 which also the Tandy Radio Shack sold a Deluxe RS-232 Pak which also used this same MOS 6551 chip. The serial port on the Dragon 64 is limited though to 38400 as the Op-Amps are slow in the Dragon 64. You probably could upgrade the Op-Amps to faster versions to get speeds up to 57600. As far as the floppy controllers go between the Dragon and the CoCo the basics have different entry points that is the biggest problem. There is a Disk Basic called HDBDOS which is used for DriveWire on the CoCo which also has been modded to have the entry points updated so it will work on the Dragon's basic. Though HDBDOS is based on Disk Basic that came with CoCo's floppy controllers. DriveWire might be something interesting for you to look into if you like using the Tandy Radio Shack Color Computer 2 and Dragon64. Also there is a upgraded CPU that you can also use in the Dragon32/64 and Tandy Radio Shack Color Computers called the HD63C09E. It has extra instructions and also is CMOS based and thus will run cooler and consume less power. Plus there are custom OS-9's that take advantage of this CPU. This OS is called NitrOS-9.
Well this supports my argument to always use the kernel calls to perform IO instead of writing your own low level function; even though that is usually more efficient and faster, it does hamper portability
The Dragon factory was located just down the road from me in Port Talbot ,Margam specifically, in South Wales.. The industrial unit was located next to the then huge Borg Warner plant. Local media made a big deal of it but after a few years closed. The factory unit was then used by Orion to manufacture video cassettes if memory serves....
A better way of looking at the parallel/serial port differences might be to think of the CoCo as having a serial port for the printer, instead of a parallel port as the Dragon does, and the Dragon having an additional interface for serial communications, such as a modem or a terminal for a second user if you're running OS/9. The CoCo serial port was entirely bit-banged and while that was fine for a printer it was not so good when used for bidirectional serial communications. Not only did it lack any control signals except for carrier detect, but bit-banging it ate a substantial amount of CPU time and set a fairly low limit on the serial rates you could achieve. This was especially noticeable when using OS/9 with an external terminal so that you could have a full 80×24 text interface. I seem to recall that at some point a serial interface cartridge with a proper UART was released, but I can't seem to find any reference to it now.
Towards the end of the Coco's life, there was a modern expansion "cartridge". If memory serves, it was still limited to 300 baud. It included a really poor terminal program. The hardware was quite rare -- I briefly owned one, but I do not recall any reviews or much advertising.
There were several serial options. Radio Shack put out an RS-232 Pak, still in the early days. It could do at least 2400 bps. Later there were a number of 3rd party serial cartridges, as well as multi-I/O boards like the Disto 4-in-1 that added a serial port, a parallel printer port, a real-time clock, and a SCSI interface on a daughter board that plugged into Disto's floppy drive controllers. The advantage of a system like that was that it didn't require an expensive Multi-Pak Interface in order to use it with a disk drive. Interestingly, very clever coding has gotten MUCH more speed out of the lowly bit-banger. Drivewire allows a modern computer to serve up disk images to a CoCo over the built-in bit-banger port, and gets up to 115kbps on a CoCo 3, or 57k on a 2 in either DECB or NitrOS-9.
@@joelavcoco Sorry, I should have been clear when I was talking about "low rates" I meant low rates _while do anything else at the same time_, such as printing the received data to the screen, scanning the keyboard for things to send, or even running other programs such as you'd want to be able to do while using a terminal to talk to OS/9. On pretty much any computer if you're willing to dedicate the entire CPU to serial transfer you can achieve reasonably high rates even with a bit-banged interface, but this is practically useful only for certain kinds of file transfer applications.
When Motorola launched the 6809, and it's associated support chips, Motorola published a reference design to show how to use them. This design is basically what the Tandy CoCo and dragon computers were based on, with minimal difference between them. Mentioned here:- Internally the CoCo 1 and CoCo 2 models are functionally identical. The core of the system is virtually identical to the reference design included in the Motorola MC6883 data sheet and consists of five LSI chips: MC6809E Microprocessor Unit (MPU) MC6883/SN74LS783/SN74LS785 Synchronous Address Multiplexor (SAM) MC6847 Video Display Generator (VDG) Two Peripheral Interface Adapters (PIA), either MC6821 or MC6822 chips zims-en.kiwix.campusafrica.gos.orange.com/wikipedia_en_all_nopic/A/Motorola_6809 www.roust-it.dk/coco/The%20MC6809%20CookBook.pdf
For what it's worth both manufacturers followed Motorola's reference design very closely and as Dragon Data also went to M$ for the OS/Basic that's the reason for the similarity. Not clones as such, more siblings. (The Dragon is no more a clone than I'm a clone of my older brother.) The primary reason why they aren't 100% compatible is for some reason when M$ sold the exact same Basic (and technical support) to both manufacturers they fiddled with the tokenising in the Dragon version. Also the Dragon's keyboard mapping is a little different.* *It's entirely possible to make a Dragon 100% Tandy compatible, and switchable between modes. A mod that had some popularity as the CoCo had more software alth9ugh you could just as easily make a CoCo Dragon compatible. It's my unverified understanding that the very close similarity of the non-Motorola inspired parts was on the advice of M$ who weren't going to waste effort on rethinking technical advice for a small company like Dragon Data. Did Dragon Data know about the CoCo? Of course. Were they trying to make a CoCo clone? No, because they didn't. But driven by the same design process they followed a path already walked by Tandy.
Loved your video, as always. Just put my hands on my first Dragon 32 and trying to learn its internals in my spare time. Definitely, I will revisit all your Dragon 32 videos and take notes !!!. I will try to purchase the coco SDC device. Thank you for the heads up :)
I remember selling both Tandy TRS80 'CoCo' - early version with the chicklet keyboard, and Dragon 32 in the small independent store where I worked in the very early 80s, and a lot more game cartridges and accessories were interchangeable - not all, but it seems things changed with these later revisions? Whatever... nice video! Thanks :-)
I was sure I'd read that the CoCo was based very directly on a reference design put out by the CPU manufacturer so the Dragon would've also been based on the same reference design. That doesn't explain why everything is so similar, but might explain why some things are so different. Perhaps the things that are different were not part of the reference design?
Clearly Dragon Data copied Tandy then swapped a couple of things just to make it incompatible. Anyone writing software for one would simply need to release a version for the other. I expect they kept the cartridge the same in the hope of reducing cartridge manufacturing costs where as swapping keyboard lines or Basic tokens just makes it different at no cost.
I almost bought a Tano Dragon at close out price 19 dollars but a paper weight but you made it a thing of beauty. I did like it in the day. I started with TI994A but it blew up and replaced with C128 USA model
The Motorola reference design was used as the basis for a videotex terminal sold breezily by RadioShack around 1980/It didn't sell very well. Radio Shack reused the videotex deign for the original Color Computer
Cool, thanks for that comparison! Now get yourself a Coco 3. It has composite and RGB outputs. Also get a ram upgrade to at least 512k and the Coco 3 will play Sierra games like King's Quest. Can the dragon do that? 🙂
Ah. That feeling. "I got this and the seller lied in the listing." "Why? Is it broken." "No, it's in perfect shape and working just as new." ".. so what's the problem?" "IT WAS SUPPOSED TO BE BROKEN SO I CAN HAVE THE FUN OF FIXING IT." Everybody thinks you are crazy, but to be honest .. USING those computers is okay, but they are old and not very useful and for just playing games you are often better off with an emulator. Working on them is where the fun is. I also repair old tube radios, but as soon as I got them working, they get kinda boring.
So the board size of the Dragon looks to be similar to that of the board size of the original (1980) CoCo. IIRC the original CoCo was just about as deep as the Dragon
Yes, it was... I used to sell these machines back in the early 80s in a small retail shop here in the UK, and they both took up similar desk-space..... Both had external power supplies back then as well. They also seemed more inter-compatible - you could use more game cartridges/tapes, and controllers between them!
@@stevesstuff1450 The original CoCo had an integral power supply, but the TRS-80 (Model 1) did have a separate power brick. That may be what you were thinking of.
This was a massive debate at school "back in the day". Nearly as passionate as "which is best: 6502 or Z80". The CoCo2's keyboard looks nice... as far as I remember the CoCo had a horrible keyboard. That 6809 book brings back memories too... I did 6502 _AND_ Z80 but my flatmate did 6809 and he had "the book of arcane knowledge".
I prefer the COCO. The keyboard is not that much worse, but the small size and built in PS are winners for me. All that said, my real favorite COCO is the COCO 3. Back in the mid-80's I used a COCO 3 with 2 double sided floppies, a Tandy 1200 baud auto answer modem, OS-9 level 2 and BASIC-09 to build a BBS system. Although I had less than 50 users, it was a great project from my perspective. Those were the days!
@@NoelsRetroLab indeed! I have an Apple II clone which is 100% compatible and when new was 1/4 of the price. So it goes to show that clones, not all, can be just as good or better
Haha, maybe, but that's how I feel with stuff like that (and I know lots of other people who do too). But with these old computers, you know that sooner or later they're going to fail. It's a fact of nature.
Coco was my first machine and started me down my career path. But I remember when the Dragon came out and was covered by the Coco magazines here in the US and being jealous at the parallel port and hardware serial (vs. the bit-banger serial on the Coco). Several years ago there was a guy in California I think selling off a bunch of new in the box Dragon Tanos he acquired somewhere - sitting in a warehouse for years I guess. They were like $70 I think and I don't know what insanity kept me from getting one! Now and then one will pop up on eBay again for several hundred dollars.
Noel I would love to see you do a wee documentary about the Spanish 8/16 bit revolution. Have seen plenty from over here in the UK of course but very little about other european countries, Spain in particular. You would be uniquely qualified for this! Anyway thanks for the fascinating content :-)
Hi Niall! That's an interesting topic that I hadn't really considered. There's quite a bit of material about it here, but aimed at the Spanish audience and in Spanish, so it could be interesting creating something like that. Thanks for the idea!
You can save the BASIC program with the A parameter (For ASCII) and it will load on the other computer. It save the basic program in ASCII instead of compressed. Take more space on the file.
It was also used for a number of Williams arcade games. A guy by the name of Glen Hewlett has recently ported the arcade Joust and Defender ROM code to the CoCo 3, and they're astounding. The FAIRLIGHT not only uses the 6809, but also runs the OS-9 real-time operating system, which also runs on the CoCo and the Dragon. You could literally run the same OS-9 binaries on a CoCo, a Dragon, or a CMI FAIRLIGHT.
All I know is the Dragon line of micro computers were designed and developed in Wales, Great Britain. I slightly remember them in the 1980's. The Tandy computers not so but I do remember the high street shops called Tandy that sold electronics in the 1980's in the UK.
A similar idea as someone who commented down below (they were talking about making an offline patcher). Would it be possible to make an inline hardware adapter to sit in between the slot and the cartridge and moved around the function calls as they came in from the cartridge, to give a dragon some better coco compatability (or vice versa)? Kinda a 'live hardware patcher'?
Looking at the Dragon keyboard matrix which is arranged electrically in ASCII order for faster key scanning and comparing that to the CoCo I would say the CoCo is the clone. The CoCo matrix looks like they took the Dragon matrix and swapped a couple of rows. This would make the key scanning code less efficient. Another clue that the CoCo is a clone of the Dragon is the Dragon has a parallel port and the CoCo uses the same IO lines to create a serial port. Where the parallel port is an obvious straight forward design the CoCo serial port is particularly cunning and would have taken much longer to develop. When the Dragon 64 came out they simply added a serial chip for the serial port.
Would it be possible to create a PCB that can switch between a coco and a dragon by just flipping a switch? I assume you can either use a PAL/GAL for the keyboard re-map, and a big enough EEPROM to place both "bios". You might lose the parallel port/serial port, but I think it's a small compromise for having a 2 in 1 machine.
I’m not sure you’re putting yourself in technology of the time. The bios was still relatively simple so that wasn’t too much to get done, but you wanted existing peripherals working with what you were building. And when you were trying to bring any new product to market, you generally either had to build up the circuits from individual components or use an integrated IC set.
How about a switchable system ROM for the dragon. I would have thought a programmable logic chip (16V8 or similar could be used to make the keyboard compatible with the Coco).
The first computer I ever used in school was a CoCo. I can't remember if it was a 1 or 2. We had no software, just the bare machine hooked up to a small TV someone scrounged up, but we typed up simple Basic programs to make it do things and it felt like the future. This would have been in 1982 or 1983.
CoCo2 was my first system; got it from a garage sale in the late '80s. I learned to program in BASIC on that thing with the help of the book it came with. Though I think if I wanted to mess around with an old system like that again, I'd stick with a fantasy console, like Pixel Vision 8 or similar. Vintage hardware is too pricey and temperamental for my taste, heh.
If the Donkey King game is coding colour in some weird NTSC way then it should be possible to build an add on to the Dragon to increase it's colours. Colour was always the Dragon's limitation more than anything else.
I want to mention that the Commodore Pet came out in 1977 and was missing from your timeline. It was the second best selling computer for a number of years, after the Tandy/Radioshack.
@@NoelsRetroLab That keyboard is a standard Cherry/ALPS keyboard layout, which was popular in a lot of computers, terminals and other data entry devices. So simply a matter of ordering the same part number, and some dark caps, with the right double shot injection mould, or a screen print legend, and then assemble it. Different keyback board, but that is simply the low volume option, using cheap soldered key contacts, instead of a custom printed film sheet that forms all keys, key dome and contacts all on a single polycarbonate sheet, that you simply fold over and heat stake into place.
@@NoelsRetroLab Tandy never shipped a CoCo with a real mechanical keyboard like either of the Dragon ones (the original Hi-Tek dovetail model on most 32s, and the later Alps SKCC which your machine has). Though the Hi-Tek keyboard was definitely available as an aftermarket upgrade in the US.
There were a few I seem to remember, probably associated with the different ROMs and direct reading of the keyboard hardware. But where they stuck to run of the mill BASIC functionality the listings were identical.
Since I didn' t own any of these computers(I had only the lame ZX Spectrum +), I can' t express any opinions(not to mention that I "lost the ball" almost from the very beginning), but I will give you only two suggestions(again): -First, can' t you build a simple circuit that will have a ZIF socket and an external power jack for the ROMs you want to program, but your programmer can' t handle their programming voltage? Along with a couple of pin headers attached to some cables? This way, you will be able to use a transistor that will use the external power thru an input from your low-power output, fed thru that transistor to the power-hungry ROM. Of course there should be some extra female headers in order to drive a cable to the specific pin you want to boost with the transistor with a cable... -And second, if the programs are virtually identical except their addresses, can' t you make a simple program which will be taking any program written for the one computer and just make the appropriate relocations to the addresses for the other computer?
The ZX Spectrum in it's various iterations was never a 'lame' computer......... It was inexpensive, and originally had a 'dodgy' keyboard, but later revisions fixed that. Come the +2 models they now had a much better sound synthesiser chip outputting to the TV that could sound really good! It had better use of colour/resolution than most other 8-bit machines at the time - as long as you could avoid the horrible colour-clash!! But it can't be denied that regardless of it's limitations, it created a whole new generation of bedroom coders and companies; many of whom are still around today - take EA for example....not everyone's favourite company now because of their inexcusable loot-box systems, but EA started back then publishing Spectrum games, and has some of the most respected coders and computer musicians associated with it, alongside the C64, of course....
As far as the different tokenizing between BASICs, it seems like the CoCo had a [C]SAVE "PROG",A which would save the program in ASCII format instead of tokenized. That might help with porting. (Oops, looks like someone already mentioned this!)
The Tandy here actually sold Drgon 64's, had them on display, but thinking about it, it might've been radio shack before they changed to tandy, not really sure.
That dragon looks to be a really cool clone of the Coco. I wonder if there is a mod to switch the BIOS ROMS to allow compatibility. I'd not be surprised if someone out there has done so. I still have my original Coco 1 and the game I liked back then was Polaris. It's a Missile Command clone. Unlike most home versions, the analog joysticks make moving the cursor to fire your missiles a lot like using a track ball. You should check it out! Great video as always!
Very likely just swapping the ROM chips would simply work, though you would not get a working keyboard without a bit of editing of the ROM, to change the mapping of key matrix to characters, which might be hard as it looks like the actual routine depends on simple bit pattern shifts, so you would need to find spare room in the ROM to put the extra bit shuffling in, as likely the existing keyboard routine memory is tightly packed.
@@SeanBZA I'm sure some clever hacker out there could have and may have already figured it out. Possibly use an Arduino or some small SBC to do a ROM emulation. I would think that you simply change out the bit pattern for the CoCo switch and no need to take up anymore memory would work too.
Betagamma Computing have done exactly this with the DraCo64 machine conversions. Both Dragon 64 and CoCo II compatible at the flick of a switch. The systems include a keyboard remapper board.
Agreed on Polaris. It's a great game, and I think it even runs on a 4K machine. (Maybe 16K?) I remember how horrible Missile Command was on the Atari 2600, but even the old 1-button, non-centering "black beauty" CoCo analog sticks made Polaris a dream to play. Great for flight sims as well.
The Dragon was a clone of the Tandy. The ROM was a bad clone as there was a bug in Dragon BASIC, in its DEFUSR(0) command. What killed both the Dragon and the Tandy was it's poor graphics chip the VDG. It was worse than what the Spectrum, Atari 800 and VIC-20 could deliver. The CPU was good, but was under-powered at 0.89MHz. Most enthusiasts today replace the 6809E with an Hitachi 6309 which is about 20 to 30% faster and clockable to 5MHz. It may be a good project to see a much faster running Tandy and at 5MHz, as some of the old games really do need the extra CPU power to be playable. There is also a poke to speed up the Tandy - POKE 65495,0 to double BASIC program speed and POKE 65494,0 will return it to normal speed.
6:09 Its not really surprising that the coco psu is so small. What's remarkable is how unnecessarily big the Dragons seems to be. I mean, you'd think at least that they could have got the AC transfomer into the case. Heck, the Beeb managed it. And at the other end of the scale the Spectrum had a 9V power brick but managed to squeeze the generation of all the nessecary voltages onto that tiny mobo. 12:46 Not sure what they were exactly, but I understand the Dragon keyboard stuff was changed for some kind of effiency/responsiveness benefit. (ruclips.net/video/0IipxReq0G8/видео.html)
Making the computer with no mains inside is very sensible and allows children to safely open the case and tinker. It also means you make another company responsible for the transformer and carry out all the product safety whilst you work on the computer independently.
I'm not sure the differences between the ROMs are entirely lawyer-inspired, any minor change to the code would shift things around, and the Dragon and CoCo used some different chips so the code for them would be slightly different, and if there's any support for the printer port on the Dragon then that will have added a huge chunk of code. Unless Dragon had specifically paid for compatibility, Microsoft wouldn't have bothered. Re-ordering the tokens is also a pretty good way for Microsoft to protect themselves from being accused of selling the customisation that Tandy undoubtedly paid for, The cartridge port being the same could just be that its possible the Dragon 32 and the original CoCo were much closer in design than the '64 and CoCo 2 you have for comparison. It's also fair to say that at the time of the Dragon 32 the (personal) computer industry was very different and "borrowing" other peoples design ideas was tolerated a lot more than it is now if it wasn't too blatant. Generally being "first to market" with a product was the strategy rather than trying to be exclusive. Tandy's computers were expensive in Europe, which is why they are so rare here, which is a shame. I used a model 1 Level 2 with expansion interface at my first job between school and uni, and I've always had a hankering to get one for sentimental reasons, but when they turn up they are either in terrible condition, or I don't have the money at the time! And I wouldn't rate my chances of getting one shipped from the 'States with the monitor intact for any reasonable amount of money!
I think it would be possible (and actually pretty easy) to write an automatic patcher to convert system call addresses from one machine to another (as long as there are equivalents on both machines).
@@NoelsRetroLab Agreed. I remember going from the CoCo2 to the CoCo3 and was BLOWN AWAY with the upgraded graphics. I spent a ton of time building a drawing program that took advantage of the high graphics modes.
Love the look and form factor of these older machines, especially the keyboards. Wish I could get a pc or Mac that was built the same.. like with the form factor of the bbc micro. That would be awesome!
I built a PC out of a BBC Micro case which I got from someone who had taken the main board and power supply. A 1U PC power supply fits in the BBC Micro case power supply space. I had to modify the case for the power connector. There’s a mini ITX board in the case and againI had to modify the back panel but it does fit nearly!
Ahhhhhh! Finally a great #septandy video to satisfy our cravings. Nice stuff on cart deep dive, and making us aware of the CoCoSDC, Adding it to the x-mas wish list! :D. Still want that seperate composite mod video, pop out a quick one pretty please! :D
Even the MC-10, Tandy's response to the ultra low cost market, tokenized BASIC differently than the Coco. The tape format was the same, but the result was garbage. It is so frustrating that the various systems were _almost_ compatible.
By using widely available components Radio Shack left themselves vulnerable to clones being made. Ironically IBM did the same thing when they made their PC, so Radio Shack returned the favor with the Tandy 1000 which was a better clone of the PC Jr.
if i remember correctly both machines are derived from a reference design developed by motorola when it was launching on the market the 6809 cpu(maybe this is why they are very similar); i've read it somewhere a lot of time a go, but i coudn't find anything now ,(im not sure it is right)
My favourite Dragon game was Speed King, I thought it played really well with an analogue joystick. I'm pretty sure it's possible to convert a Dragon to a CoCo (or vice versa) by changing the ROM and using an adapter for the keyboard connector. I have a vague memory of reading about switchable adapters that could do both at the same time.
amazing comparison always wondered if they were same amd wanted to know if games worked on either system thanks for working that out for me i stick with my 2 dragons :)
If the cart difference are just rom call addresses, shouldn't a hardware lookup table be able to make the translation on the fly? Sure, it is an extra eeprom, or mcu but we are playing the "what if" game.
Why you don't just make an adapter to switch between coco rom and dragon rom? The keyboard should be remapped too of course but is definitively doable.
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Both computers are actually based on a reference design from Motorola, the Microchroma 68, featuring a version of the MEK6800D2 MikBug monitor called TVbug. This was essentially what is in the coco (and dragon) computer. Tandy used this base design to create a Videotex terminal for farmers called the AgVision, and if you google for that you will see its actually a blue coco, it even has facilities for what later became its cartridge connector. What I want to say is that Tandy cannot claim ownership of the CoCo's architecture as it not theirs, its Motorola's. They simply took the Microchroma 68 design put it in a somewhat nice case and replaced TVbug with a BASIC written by Microsoft.
If you have a T1 VDG in the Coco, try this: POKE 359,57:POKE 65314,80. If the border turns green, and SHIFT-0 toggles between true upper and lowercase letters (as you type them), then you truly do have a T1. There is a version of OS-9 Level 1 that supports that fully, as well as numerous terminal programs, etc. Also, there is a trick to convert BASIC programs between them without retyping them (or using special utilities): Save them in ASCII format (for example CSAVE "PROGRAM",A). It is slower, but it doesn't tokenize. Also, one thing that is completely different is the disk drive ROM and disk drive formats; the Coco's use granules (9 sector blocks) while the Dragon uses actual sectors, and also supports >35 tracks. (The disk controllers on both can handle up to 80 tracks and double sided just fine; it's the Disk Extended BASIC vs. Dragon DOS ROM's that are completely different). Also, the CocoSDC also emulates hard drives as well (the Coco 3 with NitrOS-9 EOU is based on that).
Yes got to love NitrOS-9 L2 on the CoCo 3 with the CoCoSDC!
I'm always impressed with how much technical information and in-depth research you present in all of your videos Noel, another great watch as usual!
Your videos keep getting better and better. Thanks Noel.
In 1983 I designed a children's computer using that same Motorola chipset, so it was pretty similar to the CoCo. But there were many differences (serial keyboard, network, Logo in ROM, no cartridge, different sound). Not long after that a bunch of CoCo clones were launched in Brazil (Prologica CP400, Codimex CD6809, Dynacom MX-1600, Engetecnica VC50, NovoTempo/LZ Color64). That made people think my machine had been a clone as well.
I seem to remember a blurb about the Dragon being designed with aid from Motorola and based on their reference design, but as you said the details are a bit too similar. I'd guess a believable scenario would be someone just handing them the schematic as a reference to the problem already being solved before.
The most telling part is that in the MC6847 datasheets they used a dedicated chip for the colour circuits, but here they've both got a dedicated circuit instead. I would think Motorola would have sold them on that chip instead of all those components.
It seems feasible that Motorola might have directed the design for increased compatability with the existing platform. When Mettoy set out to create a computer it doesn't seem like they had a lot of requirements except "we need it yesterday". And Motorola had worked together with Tandy to create the Coco.
I didn't play a lot of games on my Coco. However, I did a lot of hardware development. I built several peripherals for it including a universal EPROM programmer, a text to speech card, and a 6809 In-Circuit emulator that worked by allowing the Coc's 6809 to take over the target system's bus. I also build a data logging card that used a small fast ADC that had a two-wire multi-device interface that I had to bit-bang. I did many other projects as well. I miss the days of direct access to hardware! As for software, my favorite programs were the assembler cart and the terminal program that allowed me to dial into my favorite BBS. Remember those?
Looks like they both came from the same reference design, so they are brothers, so to speak.
The chipset and the Microsoft Basic emulator put restrictions on the way the system is designed, but Dragon64 design team did take advantage of what little leeway their was and distanced themselves from the Tandy machines. Legal fights based on forced commonality would not have much teeth in court.
Thanks for the comparison, good stuff!
Cheers,
Excellent Work as usual. Owning a Dragon 32 and CoCo2 this video was particularly interesting for me. I like the Dragon more myself as well. Just because most people here don't know it exists. Awaiting a CoCoSDC, Glad to know it has your seal of approval.
Thank you! Now I'm curious about the Tano Dragon and what's different about it. Up until a few years ago you could still buy them new old stock for about $100 I think, but they've been out for a while.
Excellent video. So clear, informative, and concise. Thanks!
Very thorough and unique approach as usually. I'm the owner of a cpc6128 and one of the things I would like is someone to make a step by step tutorial on how to make the simplest rom expansion, just one rom using one eprom / eeprom. As few components as possible. There are many products that do this but diy is what I'm looking for. The already available designs, include 4 or 6 roms and really, you need to solder a very large number of cables making them unattractive and cumbersome. I wish you consider this for a future tutorial.
i wanna know how/if its possible.. to convert it from the multiple DRAM chips to a single SRAM..or have a rom expansion that takes over from main ram from the get go.. (im having trouble sourcing 4164s atm)
I also belong to the “disappointed when it works because I wanted to fix it” camp.
Love it all, especially the 6809 disassembly and comparison. Brings back memories.
Thank you! It was fun confirming why those few bytes were different.
The 6809 was an amazing CPU for its time, far superior to the 6502 I would say. 6809 assembly language is actually fun to program. Apparently the price was a stumbling block and so it was rarely used. A shame really.
It has more accumulators, more (16-bit) index registers, more (16-bit) stack pointers, more addressing modes, hardware multiply, and an 8-bit register that allows you to position the Direct Page anywhere in memory.
@@joelavcoco Indeed. It's a shame the 6809 didn't see more use. Imagine how much better the software would have been back in the day. They did remarkable things with the 6502, but at the end of the day you can't get blood from a stone.
My favourite game for the Dragon32 was Manic Miner, which I used to play constantly. I've recently managed to find Dos version of this which I am now playing and once again i'm hooked
Excellent comparative review - looking forward to seeing the 200 machines.
You and me both! 😃 (Although I believe it's somewhat disappointing that it's mostly a case change only).
@@NoelsRetroLab The 200 does have an additional character ROM board to take advantage of this unused feature of the VDG (see data sheet).
Both of these don't look like much but they actually feature the best (and most expensive) 8-bit CPU ever. The 6809 is like the grand daddy of the 6502 and very much prepared to run a real multi-tasking operating system as we know it today.
6502 was the cheapest 8 bit MPU. Nothing else about it is remarkable. The 6809 is a joy to program for in comparison.
IMHO I think it had the best basic, and a very easy to use assembler
@@lawrencemanning As is probably clear to anybody who's written just a few thousand lines of assembler for each, the 6502 is remarkably well designed, with a number of design choices that were clear improvements over its inspiration the 6800 (not the 6809, which came years later) even when you're not taking cost into account.
Among other things these include removing some of the most annoying behaviours of the 6800 (setting flags on stores, not being able to push the index register), being little-endian to save a cycle on any instruction involving a 16-bit address calculation, and being able to do indirect memory access through an address in any zero page location, rather than just through a single index register.
Though the cost considerations seem to have precluded making a CPU that was better in every respect than the 6800, the 6502 designers did produce a CPU that was faster and had more powerful addressing modes, as well as being well under half the price.
The 6809 is an upgraded 6800, which is the 8-bit precursor to the 68000.
The greatest thing about the 6809/6502 was the PCR (Program Counter Relative) data instructions, which meant that it was possible to make a program completely relocatable in memory.
I used that feature in a machine-code program which was designed to allow a BASIC program to print the entire IBM extended ASCII character set on the "high resolution" display on the COCO.
The data for the characters took up more space than the program did, yet the program had advanced features such as allowing the BASIC program to redefine characters without having to know where to POKE the character definitions in memory; print characters in reverse video; reposition the cursor; clear the screen and home the cursor and so on.
I had both the VIC20 and CC3. I can say today I am a firmware and hardware engineer... Those days as a kid typing in games from a magazine got me intreated in programming and engineering.. Loved those days!!!
Two videos in a week im in heaven!! Time to nerd out with Noel
You know you are total geek when you are disappointed when you turn on an old computer and it works! Great vid.
"And when plugged in, it worked, how disappointing"
Haven't heard that sentence before.
You obviously haven't watched the "My Mate Vince" channel 😁
Great video!
Thank you for sharing!
The Tandy Radio Shack Color Computer 2 is what I started with. Though the model I had used the standard 6847 not the T1 version.
As far as the Dragon64 goes the serial chip is a MOS 6551 which also the Tandy Radio Shack sold a Deluxe RS-232 Pak which also used this same MOS 6551 chip.
The serial port on the Dragon 64 is limited though to 38400 as the Op-Amps are slow in the Dragon 64. You probably could upgrade the Op-Amps to faster versions to get speeds up to 57600.
As far as the floppy controllers go between the Dragon and the CoCo the basics have different entry points that is the biggest problem. There is a Disk Basic called HDBDOS which is used for DriveWire on the CoCo which also has been modded to have the entry points updated so it will work on the Dragon's basic. Though HDBDOS is based on Disk Basic that came with CoCo's floppy controllers.
DriveWire might be something interesting for you to look into if you like using the Tandy Radio Shack Color Computer 2 and Dragon64.
Also there is a upgraded CPU that you can also use in the Dragon32/64 and Tandy Radio Shack Color Computers called the HD63C09E. It has extra instructions and also is CMOS based and thus will run cooler and consume less power. Plus there are custom OS-9's that take advantage of this CPU. This OS is called NitrOS-9.
Well this supports my argument to always use the kernel calls to perform IO instead of writing your own low level function; even though that is usually more efficient and faster, it does hamper portability
"Hopefully those won't work the first time I power them on."
-The Tinkerer's Motto
I have the D32, D64 and the Tano. The great thing with the Tano is that you actually get the artificial coloUrs, like on the CoCo.
The Dragon factory was located just down the road from me in Port Talbot ,Margam specifically, in South Wales.. The industrial unit was located next to the then huge Borg Warner plant. Local media made a big deal of it but after a few years closed. The factory unit was then used by Orion to manufacture video cassettes if memory serves....
A better way of looking at the parallel/serial port differences might be to think of the CoCo as having a serial port for the printer, instead of a parallel port as the Dragon does, and the Dragon having an additional interface for serial communications, such as a modem or a terminal for a second user if you're running OS/9.
The CoCo serial port was entirely bit-banged and while that was fine for a printer it was not so good when used for bidirectional serial communications. Not only did it lack any control signals except for carrier detect, but bit-banging it ate a substantial amount of CPU time and set a fairly low limit on the serial rates you could achieve. This was especially noticeable when using OS/9 with an external terminal so that you could have a full 80×24 text interface.
I seem to recall that at some point a serial interface cartridge with a proper UART was released, but I can't seem to find any reference to it now.
Towards the end of the Coco's life, there was a modern expansion "cartridge". If memory serves, it was still limited to 300 baud. It included a really poor terminal program. The hardware was quite rare -- I briefly owned one, but I do not recall any reviews or much advertising.
There were several serial options. Radio Shack put out an RS-232 Pak, still in the early days. It could do at least 2400 bps. Later there were a number of 3rd party serial cartridges, as well as multi-I/O boards like the Disto 4-in-1 that added a serial port, a parallel printer port, a real-time clock, and a SCSI interface on a daughter board that plugged into Disto's floppy drive controllers. The advantage of a system like that was that it didn't require an expensive Multi-Pak Interface in order to use it with a disk drive.
Interestingly, very clever coding has gotten MUCH more speed out of the lowly bit-banger. Drivewire allows a modern computer to serve up disk images to a CoCo over the built-in bit-banger port, and gets up to 115kbps on a CoCo 3, or 57k on a 2 in either DECB or NitrOS-9.
@@joelavcoco Sorry, I should have been clear when I was talking about "low rates" I meant low rates _while do anything else at the same time_, such as printing the received data to the screen, scanning the keyboard for things to send, or even running other programs such as you'd want to be able to do while using a terminal to talk to OS/9.
On pretty much any computer if you're willing to dedicate the entire CPU to serial transfer you can achieve reasonably high rates even with a bit-banged interface, but this is practically useful only for certain kinds of file transfer applications.
When Motorola launched the 6809, and it's associated support chips, Motorola published a reference design to show how to use them. This design is basically what the Tandy CoCo and dragon computers were based on, with minimal difference between them.
Mentioned here:-
Internally the CoCo 1 and CoCo 2 models are functionally identical. The core of the system is virtually identical to the reference design included in the Motorola MC6883 data sheet and consists of five LSI chips:
MC6809E Microprocessor Unit (MPU)
MC6883/SN74LS783/SN74LS785 Synchronous Address Multiplexor (SAM)
MC6847 Video Display Generator (VDG)
Two Peripheral Interface Adapters (PIA), either MC6821 or MC6822 chips
zims-en.kiwix.campusafrica.gos.orange.com/wikipedia_en_all_nopic/A/Motorola_6809
www.roust-it.dk/coco/The%20MC6809%20CookBook.pdf
Very nice video Noel, interessting to see the differences! Btw, I try to deliver you the thermal images by the thermal cam on this weekend :-D Michael
For what it's worth both manufacturers followed Motorola's reference design very closely and as Dragon Data also went to M$ for the OS/Basic that's the reason for the similarity. Not clones as such, more siblings. (The Dragon is no more a clone than I'm a clone of my older brother.)
The primary reason why they aren't 100% compatible is for some reason when M$ sold the exact same Basic (and technical support) to both manufacturers they fiddled with the tokenising in the Dragon version. Also the Dragon's keyboard mapping is a little different.*
*It's entirely possible to make a Dragon 100% Tandy compatible, and switchable between modes. A mod that had some popularity as the CoCo had more software alth9ugh you could just as easily make a CoCo Dragon compatible.
It's my unverified understanding that the very close similarity of the non-Motorola inspired parts was on the advice of M$ who weren't going to waste effort on rethinking technical advice for a small company like Dragon Data. Did Dragon Data know about the CoCo? Of course. Were they trying to make a CoCo clone? No, because they didn't. But driven by the same design process they followed a path already walked by Tandy.
Loved your video, as always. Just put my hands on my first Dragon 32 and trying to learn its internals in my spare time. Definitely, I will revisit all your Dragon 32 videos and take notes !!!. I will try to purchase the coco SDC device. Thank you for the heads up :)
As always nice and informative videos. My favourite comment is "hopefully those won't work the first time I power them on"
😃 Thank you!
I remember selling both Tandy TRS80 'CoCo' - early version with the chicklet keyboard, and Dragon 32 in the small independent store where I worked in the very early 80s, and a lot more game cartridges and accessories were interchangeable - not all, but it seems things changed with these later revisions?
Whatever... nice video! Thanks :-)
I was sure I'd read that the CoCo was based very directly on a reference design put out by the CPU manufacturer so the Dragon would've also been based on the same reference design. That doesn't explain why everything is so similar, but might explain why some things are so different. Perhaps the things that are different were not part of the reference design?
Clearly Dragon Data copied Tandy then swapped a couple of things just to make it incompatible. Anyone writing software for one would simply need to release a version for the other. I expect they kept the cartridge the same in the hope of reducing cartridge manufacturing costs where as swapping keyboard lines or Basic tokens just makes it different at no cost.
However looking at the more elegant Dragon keyboard matrix it looks like the Tandy swapped a couple of rows to make itself different.
I almost bought a Tano Dragon at close out price 19 dollars but a paper weight but you made it a thing of beauty. I did like it in the day. I started with TI994A but it blew up and replaced with C128 USA model
The Motorola reference design was used as the basis for a videotex terminal sold breezily by RadioShack around 1980/It didn't sell very well. Radio Shack reused the videotex deign for the original Color Computer
Cool, thanks for that comparison! Now get yourself a Coco 3. It has composite and RGB outputs. Also get a ram upgrade to at least 512k and the Coco 3 will play Sierra games like King's Quest. Can the dragon do that? 🙂
Ah. That feeling.
"I got this and the seller lied in the listing."
"Why? Is it broken."
"No, it's in perfect shape and working just as new."
".. so what's the problem?"
"IT WAS SUPPOSED TO BE BROKEN SO I CAN HAVE THE FUN OF FIXING IT."
Everybody thinks you are crazy, but to be honest .. USING those computers is okay, but they are old and not very useful and for just playing games you are often better off with an emulator. Working on them is where the fun is.
I also repair old tube radios, but as soon as I got them working, they get kinda boring.
So the board size of the Dragon looks to be similar to that of the board size of the original (1980) CoCo. IIRC the original CoCo was just about as deep as the Dragon
Yes, it was... I used to sell these machines back in the early 80s in a small retail shop here in the UK, and they both took up similar desk-space..... Both had external power supplies back then as well. They also seemed more inter-compatible - you could use more game cartridges/tapes, and controllers between them!
@@stevesstuff1450 The original CoCo had an integral power supply, but the TRS-80 (Model 1) did have a separate power brick. That may be what you were thinking of.
This was a massive debate at school "back in the day". Nearly as passionate as "which is best: 6502 or Z80". The CoCo2's keyboard looks nice... as far as I remember the CoCo had a horrible keyboard. That 6809 book brings back memories too... I did 6502 _AND_ Z80 but my flatmate did 6809 and he had "the book of arcane knowledge".
I prefer the COCO. The keyboard is not that much worse, but the small size and built in PS are winners for me. All that said, my real favorite COCO is the COCO 3.
Back in the mid-80's I used a COCO 3 with 2 double sided floppies, a Tandy 1200 baud auto answer modem, OS-9 level 2 and BASIC-09 to build a BBS system. Although I had less than 50 users, it was a great project from my perspective. Those were the days!
Fair enough. I'm definitely looking forward to trying out a CoCo 3 sometime. Everybody raves about it.
Interesting video were the clone is actually better than the original. Nicely done!
Right. This is not the case at all of "it's a clone so it must be bad".
@@NoelsRetroLab indeed! I have an Apple II clone which is 100% compatible and when new was 1/4 of the price. So it goes to show that clones, not all, can be just as good or better
Great video Noel. There is something a little bit wrong about being disappointed when you buy a computer on eBay and it works.. ;)
Haha, maybe, but that's how I feel with stuff like that (and I know lots of other people who do too). But with these old computers, you know that sooner or later they're going to fail. It's a fact of nature.
Coco was my first machine and started me down my career path. But I remember when the Dragon came out and was covered by the Coco magazines here in the US and being jealous at the parallel port and hardware serial (vs. the bit-banger serial on the Coco). Several years ago there was a guy in California I think selling off a bunch of new in the box Dragon Tanos he acquired somewhere - sitting in a warehouse for years I guess. They were like $70 I think and I don't know what insanity kept me from getting one! Now and then one will pop up on eBay again for several hundred dollars.
ahh a fresh episode of Noel , time to kick back and geek out.
There is hardly anything more disappointing than discovering that all the stuff in your latest "untested/for parts" haul is actually working...
Noel I would love to see you do a wee documentary about the Spanish 8/16 bit revolution. Have seen plenty from over here in the UK of course but very little about other european countries, Spain in particular. You would be uniquely qualified for this! Anyway thanks for the fascinating content :-)
Hi Niall! That's an interesting topic that I hadn't really considered. There's quite a bit of material about it here, but aimed at the Spanish audience and in Spanish, so it could be interesting creating something like that. Thanks for the idea!
You can save the BASIC program with the A parameter (For ASCII) and it will load on the other computer. It save the basic program in ASCII instead of compressed. Take more space on the file.
The 6809E was also used in CMI's FAIRLIGHT V.
It was also used for a number of Williams arcade games. A guy by the name of Glen Hewlett has recently ported the arcade Joust and Defender ROM code to the CoCo 3, and they're astounding.
The FAIRLIGHT not only uses the 6809, but also runs the OS-9 real-time operating system, which also runs on the CoCo and the Dragon. You could literally run the same OS-9 binaries on a CoCo, a Dragon, or a CMI FAIRLIGHT.
All I know is the Dragon line of micro computers were designed and developed in Wales, Great Britain. I slightly remember them in the 1980's. The Tandy computers not so but I do remember the high street shops called Tandy that sold electronics in the 1980's in the UK.
A similar idea as someone who commented down below (they were talking about making an offline patcher). Would it be possible to make an inline hardware adapter to sit in between the slot and the cartridge and moved around the function calls as they came in from the cartridge, to give a dragon some better coco compatability (or vice versa)? Kinda a 'live hardware patcher'?
Great video. Very interesting.
Next step: build a cartridge that maps ROM calls from one system to the other on the fly 😉.
OMG a Pen&Paper RPG Character sheet! How all these nerdy hobbies go so well with each other. :D
Good eye! Next question: What RPG system? 😃
@@NoelsRetroLab Not sure, I am not into Chtulhu stuff. :D
Looking at the Dragon keyboard matrix which is arranged electrically in ASCII order for faster key scanning and comparing that to the CoCo I would say the CoCo is the clone.
The CoCo matrix looks like they took the Dragon matrix and swapped a couple of rows. This would make the key scanning code less efficient.
Another clue that the CoCo is a clone of the Dragon is the Dragon has a parallel port and the CoCo uses the same IO lines to create a serial port. Where the parallel port is an obvious straight forward design the CoCo serial port is particularly cunning and would have taken much longer to develop.
When the Dragon 64 came out they simply added a serial chip for the serial port.
Would it be possible to create a PCB that can switch between a coco and a dragon by just flipping a switch? I assume you can either use a PAL/GAL for the keyboard re-map, and a big enough EEPROM to place both "bios". You might lose the parallel port/serial port, but I think it's a small compromise for having a 2 in 1 machine.
I’m not sure you’re putting yourself in technology of the time. The bios was still relatively simple so that wasn’t too much to get done, but you wanted existing peripherals working with what you were building. And when you were trying to bring any new product to market, you generally either had to build up the circuits from individual components or use an integrated IC set.
How about a switchable system ROM for the dragon. I would have thought a programmable logic chip (16V8 or similar could be used to make the keyboard compatible with the Coco).
The first computer I ever used in school was a CoCo. I can't remember if it was a 1 or 2. We had no software, just the bare machine hooked up to a small TV someone scrounged up, but we typed up simple Basic programs to make it do things and it felt like the future. This would have been in 1982 or 1983.
CoCo2 was my first system; got it from a garage sale in the late '80s. I learned to program in BASIC on that thing with the help of the book it came with. Though I think if I wanted to mess around with an old system like that again, I'd stick with a fantasy console, like Pixel Vision 8 or similar. Vintage hardware is too pricey and temperamental for my taste, heh.
12:45 lawyers again. But probably the keyboard manufacturers lawyers instead of dragon's
If the Donkey King game is coding colour in some weird NTSC way then it should be possible to build an add on to the Dragon to increase it's colours. Colour was always the Dragon's limitation more than anything else.
I want to mention that the Commodore Pet came out in 1977 and was missing from your timeline. It was the second best selling computer for a number of years, after the Tandy/Radioshack.
I never noticed that the keyboards were identical!!! Were they made by the same manufacturer perhaps?
Probably! They probably just called up Tandy's keyboard supplier and said "give us 10000 of the same one as those other guys... but in dark, please" 😃
@@NoelsRetroLab That keyboard is a standard Cherry/ALPS keyboard layout, which was popular in a lot of computers, terminals and other data entry devices. So simply a matter of ordering the same part number, and some dark caps, with the right double shot injection mould, or a screen print legend, and then assemble it. Different keyback board, but that is simply the low volume option, using cheap soldered key contacts, instead of a custom printed film sheet that forms all keys, key dome and contacts all on a single polycarbonate sheet, that you simply fold over and heat stake into place.
@@NoelsRetroLab Tandy never shipped a CoCo with a real mechanical keyboard like either of the Dragon ones (the original Hi-Tek dovetail model on most 32s, and the later Alps SKCC which your machine has). Though the Hi-Tek keyboard was definitely available as an aftermarket upgrade in the US.
Ed Snider, who sells the CoCoSDC, also makes a modern mechanical keyboard replacement for the CoCo.
Yes, these were different times. It probably helped, that it was before the internet - so information traveled very slow.
You're right. And maybe Tandy wasn't looking too hard at the European market. But it's still shocking how close they were.
@@NoelsRetroLab The earlier TRS80 computers were sold in the UK.
The old Input magazine in the UK had example programs the were for Dragon and Tandy, can’t remember if there were any changes between them.
There were a few I seem to remember, probably associated with the different ROMs and direct reading of the keyboard hardware. But where they stuck to run of the mill BASIC functionality the listings were identical.
Great comparison video
Since I didn' t own any of these computers(I had only the lame ZX Spectrum +), I can' t express any opinions(not to mention that I "lost the ball" almost from the very beginning), but I will give you only two suggestions(again):
-First, can' t you build a simple circuit that will have a ZIF socket and an external power jack for the ROMs you want to program, but your programmer can' t handle their programming voltage? Along with a couple of pin headers attached to some cables? This way, you will be able to use a transistor that will use the external power thru an input from your low-power output, fed thru that transistor to the power-hungry ROM. Of course there should be some extra female headers in order to drive a cable to the specific pin you want to boost with the transistor with a cable...
-And second, if the programs are virtually identical except their addresses, can' t you make a simple program which will be taking any program written for the one computer and just make the appropriate relocations to the addresses for the other computer?
The ZX Spectrum in it's various iterations was never a 'lame' computer.........
It was inexpensive, and originally had a 'dodgy' keyboard, but later revisions fixed that. Come the +2 models they now had a much better sound synthesiser chip outputting to the TV that could sound really good! It had better use of colour/resolution than most other 8-bit machines at the time - as long as you could avoid the horrible colour-clash!!
But it can't be denied that regardless of it's limitations, it created a whole new generation of bedroom coders and companies; many of whom are still around today - take EA for example....not everyone's favourite company now because of their inexcusable loot-box systems, but EA started back then publishing Spectrum games, and has some of the most respected coders and computer musicians associated with it, alongside the C64, of course....
@@stevesstuff1450 Yes, since +2 they started putting more humane keyboards, but I, personally, had the +...
As far as the different tokenizing between BASICs, it seems like the CoCo had a [C]SAVE "PROG",A which would save the program in ASCII format instead of tokenized. That might help with porting. (Oops, looks like someone already mentioned this!)
Wow. I never knew there were PAL CoCos! I always learn something here.
Very interesting. I did not know about that similarities.
You know it's a Noel video when he is disappointed when a computer works!
The Tandy here actually sold Drgon 64's, had them on display, but thinking about it, it might've been radio shack before they changed to tandy, not really sure.
That dragon looks to be a really cool clone of the Coco. I wonder if there is a mod to switch the BIOS ROMS to allow compatibility. I'd not be surprised if someone out there has done so.
I still have my original Coco 1 and the game I liked back then was Polaris. It's a Missile Command clone. Unlike most home versions, the analog joysticks make moving the cursor to fire your missiles a lot like using a track ball. You should check it out! Great video as always!
Very likely just swapping the ROM chips would simply work, though you would not get a working keyboard without a bit of editing of the ROM, to change the mapping of key matrix to characters, which might be hard as it looks like the actual routine depends on simple bit pattern shifts, so you would need to find spare room in the ROM to put the extra bit shuffling in, as likely the existing keyboard routine memory is tightly packed.
@@SeanBZA I'm sure some clever hacker out there could have and may have already figured it out. Possibly use an Arduino or some small SBC to do a ROM emulation. I would think that you simply change out the bit pattern for the CoCo switch and no need to take up anymore memory would work too.
Betagamma Computing have done exactly this with the DraCo64 machine conversions. Both Dragon 64 and CoCo II compatible at the flick of a switch. The systems include a keyboard remapper board.
@@mikemiller1208 I knew someone out there has done it before. They are practically the same machine with minor differences.
Agreed on Polaris. It's a great game, and I think it even runs on a 4K machine. (Maybe 16K?) I remember how horrible Missile Command was on the Atari 2600, but even the old 1-button, non-centering "black beauty" CoCo analog sticks made Polaris a dream to play. Great for flight sims as well.
The VIC-1001 was released in Japan in October 1980, which had Katakana symbols - the architecture was the VIC-20 otherwise.
The Dragon was a clone of the Tandy. The ROM was a bad clone as there was a bug in Dragon BASIC, in its DEFUSR(0) command. What killed both the Dragon and the Tandy was it's poor graphics chip the VDG. It was worse than what the Spectrum, Atari 800 and VIC-20 could deliver. The CPU was good, but was under-powered at 0.89MHz. Most enthusiasts today replace the 6809E with an Hitachi 6309 which is about 20 to 30% faster and clockable to 5MHz. It may be a good project to see a much faster running Tandy and at 5MHz, as some of the old games really do need the extra CPU power to be playable. There is also a poke to speed up the Tandy - POKE 65495,0 to double BASIC program speed and POKE 65494,0 will return it to normal speed.
6:09 Its not really surprising that the coco psu is so small. What's remarkable is how unnecessarily big the Dragons seems to be.
I mean, you'd think at least that they could have got the AC transfomer into the case. Heck, the Beeb managed it.
And at the other end of the scale the Spectrum had a 9V power brick but managed to squeeze the generation of all the nessecary voltages onto that tiny mobo.
12:46 Not sure what they were exactly, but I understand the Dragon keyboard stuff was changed for some kind of effiency/responsiveness benefit. (ruclips.net/video/0IipxReq0G8/видео.html)
Making the computer with no mains inside is very sensible and allows children to safely open the case and tinker. It also means you make another company responsible for the transformer and carry out all the product safety whilst you work on the computer independently.
Brilliant video, as always!
I'm not sure the differences between the ROMs are entirely lawyer-inspired, any minor change to the code would shift things around, and the Dragon and CoCo used some different chips so the code for them would be slightly different, and if there's any support for the printer port on the Dragon then that will have added a huge chunk of code. Unless Dragon had specifically paid for compatibility, Microsoft wouldn't have bothered. Re-ordering the tokens is also a pretty good way for Microsoft to protect themselves from being accused of selling the customisation that Tandy undoubtedly paid for,
The cartridge port being the same could just be that its possible the Dragon 32 and the original CoCo were much closer in design than the '64 and CoCo 2 you have for comparison. It's also fair to say that at the time of the Dragon 32 the (personal) computer industry was very different and "borrowing" other peoples design ideas was tolerated a lot more than it is now if it wasn't too blatant. Generally being "first to market" with a product was the strategy rather than trying to be exclusive.
Tandy's computers were expensive in Europe, which is why they are so rare here, which is a shame. I used a model 1 Level 2 with expansion interface at my first job between school and uni, and I've always had a hankering to get one for sentimental reasons, but when they turn up they are either in terrible condition, or I don't have the money at the time! And I wouldn't rate my chances of getting one shipped from the 'States with the monitor intact for any reasonable amount of money!
I think it would be possible (and actually pretty easy) to write an automatic patcher to convert system call addresses from one machine to another (as long as there are equivalents on both machines).
The Coco 3 has greatly improved graphics.
Yes, it does. I'm definitely curious to check that one out one day.
@@NoelsRetroLab Agreed. I remember going from the CoCo2 to the CoCo3 and was BLOWN AWAY with the upgraded graphics. I spent a ton of time building a drawing program that took advantage of the high graphics modes.
Love the look and form factor of these older machines, especially the keyboards. Wish I could get a pc or Mac that was built the same.. like with the form factor of the bbc micro. That would be awesome!
I built a PC out of a BBC Micro case which I got from someone who had taken the main board and power supply. A 1U PC power supply fits in the BBC Micro case power supply space. I had to modify the case for the power connector. There’s a mini ITX board in the case and againI had to modify the back panel but it does fit nearly!
Ahhhhhh! Finally a great #septandy video to satisfy our cravings. Nice stuff on cart deep dive, and making us aware of the CoCoSDC, Adding it to the x-mas wish list! :D. Still want that seperate composite mod video, pop out a quick one pretty please! :D
Even the MC-10, Tandy's response to the ultra low cost market, tokenized BASIC differently than the Coco. The tape format was the same, but the result was garbage. It is so frustrating that the various systems were _almost_ compatible.
By using widely available components Radio Shack left themselves vulnerable to clones being made. Ironically IBM did the same thing when they made their PC, so Radio Shack returned the favor with the Tandy 1000 which was a better clone of the PC Jr.
if i remember correctly both machines are derived from a reference design developed by motorola when it was launching on the market the 6809 cpu(maybe this is why they are very similar); i've read it somewhere a lot of time a go, but i coudn't find anything now ,(im not sure it is right)
My favourite Dragon game was Speed King, I thought it played really well with an analogue joystick.
I'm pretty sure it's possible to convert a Dragon to a CoCo (or vice versa) by changing the ROM and using an adapter for the keyboard connector. I have a vague memory of reading about switchable adapters that could do both at the same time.
I suspected the hobbyist community in the UK figured something out: a lot of CoCo software out there compared to the Dragon I think.
Speed kong
Putting header pins in an IC socket will bent the IC socket's 'springs' beyond repair. It will never take an IC again - reliably. [2c]
May be the different keyboard connections was for avoiding people to put a copy of the coco ROM into the dragon...
It's possible, although I'm not seeing a reason why Dragon Data would care about that particular point. But who knows!
Meteoroids is pronounced ‘mee-tee-or-oids’ A meteoroid is a small asteroid, so more cheekiness! 🤣
Great video! Thank you!
amazing comparison always wondered if they were same amd wanted to know if games worked on either system thanks for working that out for me i stick with my 2 dragons :)
god damn it i was was minding my own business and chewing on chicken bones. You just had to make jokes didn't you.
If the cart difference are just rom call addresses, shouldn't a hardware lookup table be able to make the translation on the fly? Sure, it is an extra eeprom, or mcu but we are playing the "what if" game.
Australia's most famous home computer, the Dick Smith system 80 was a knockoff of the TRS 80. Even the name gives it away.
I made my own ROM cartridge PCB back in 1984.
YM221-22828 is a Yamaha DIP chip
Why you don´t make a toaster of one of these? A Commodore 16 set with datasette is easy to find on the german page from ebay.
Why you don't just make an adapter to switch between coco rom and dragon rom? The keyboard should be remapped too of course but is definitively doable.
Does your Co-Co have the extended BASIC?
Im watching this in October :)