Z80 Computer - Mark 2
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- Опубликовано: 8 сен 2024
- A video giving a rough overview of a a completely new design for a Z80 computer I've been working on.
I have not yet had the time to tidy up the code or draw schematics for a proper release, though I'd be happy to try to answer any specific questions you have!
In the meantime, information, source code and the schematic for the dsPIC33 VDC can be
found at the following links:
benryves.com/jo...
benryves.com/bi...
benryves.com/bi...
My version of CP/M 3 was put together from the developer's build directory found on
www.cpm.z80.de/...
Excellent video. Highly entertaining.
It is refreshing to hear such cleanly spoken English.
I'm a fellow computer hobbiest, and fan. I am really a fan, not that many not that many people build what can be called a full fledged computer. It's really cool and quite frankly amazing, for this I applaud you.
I recently decided to make my own simple Z80 computer, using slightly modern parts like ATmega328p (with an Arduino bootloader) as an IO controller and so on... (I'm only in a learning hw stage and a bit in the planning stage so far...) YT recommended me this and I'm stunned. Excellent work and presentation. Very advanced from my perspective. Congratulations! (10+ y old video, but still...)
Thank you very much, and good luck with your own project! :)
Thank you for the kind comments - that sounds like a great project you're working on. :-) I think my design is probably a bit too store-bought for you if you're designing your own CPU (considering the large AVR doing a lot of the work) but I look forwards to seeing what you come up with.
Very nice work. I actually started in electronics hardware and migrated to software when these chips were introduced in 1970s. Construction today is much easier, thanks to a wide range of logic and special function ICs. Cheers!
I just got this in my recommended I don't know why but great video
This is absolutely amazing! I'm currently using a Micro Professor (MPF-1a) to learn Z80 assembly. Its a trainer board made by Multi tech in the early 1980s. There is a 2K monitor program and the display is a bank of 6 7 segment figures. All code is entered as Z80 opcodes (i.e to load $ff into register A (ld a,$ff) you enter 3E FF... etc etc... I'm currently trying to get a 16 x 2 LCD working. I have the LCD connected to a Z80 PIO chip using the PIO's PORTB to control CE, RS and RW and am using PORTA for the LCD data lines (D0-D7). So far I have a flashing cursor but text output is proving to be a challenge... I think what you have done here is really lovely!
Very cool build! I am hoping to work with a z80 soon, glad to see how you did it to get some ideas!
That was such fun! I like the choice of peripherals. Having the venerable old z80 in the midst of all of that modern silicon was like letting a caveman pilot a flying saucer! I like your sense of humor too! Thank you for posting this.
Old video but very interesting. I like the idea of using a paper template for the connections and putting the wire down before the sockets.
Ah, man! This is great! Excellent project. I grew up on the Z80 (ZX Spectrum - yep, I'm from the 80's) and it was the first assembler I knew.
What you created, is one of my dreams, I have been working on it for a few months now... =)
It is really impressive, congrats!
Nicely done even back then ✨✨👌
All machine-specific code in CP/M is stored in a single module, the BIOS. To port CP/M to a different machine all you need to do is write your custom BIOS (which only has a handful of functions in it). The CP/M 3 developer directory (which can be found online) has all the tools you should need to build the BIOS and turn it and the BDOS into the CPM3.SYS file your machine boots from (GENCPM). It's a bit much to answer in a RUclips comment, though!
This video is DOPE AF OMG you have a personality, thank you so much for being a person, cool retro camera BTW, kek. You deserve a subscriber
just wow, plus you added the chip tunes at the end :) I can believe you know so much about the Z80 mate, I'm lost as to how you got BBC basic up and running, let alone building the motherboard, video and sound card!
Really cool, keep it up !
@shaurz I prefer it now as you can get more parts into a smaller area. Fine Kynar wire works well in my experience - good luck, and thanks for your comments!
@blackcountryme Thanks for your kind comments! I only got to use BBC computers at school too, though they did leave a lasting impression. Colour would certainly be a good addition, if I could find the memory.
The SN76489 sound chip I'm emulating is very primitive in comparison to the others you named but a talented musician/programmer could certainly squeeze some good tunes out of it!
I'll have to see about that beard... ;-) Cheers!
Thank you very much for your kind comment! At the moment I'm facing my biggest challenge, how to get work projects done whilst leaving some time to work on my personal ones. I haven't quite cracked it yet but you'll probably hear from me if I ever do.
It remains cool to the touch. The only chips that get warm are the 5V regulator (though not warm enough to warrant an additional heatsink) and the logic chips used to generate the clock signal (20MHz divided to 10MHz).
@TheOneToxic The flip-flop asserts /WAIT as soon as /IORQ goes low; the Z80 samples /WAIT on the falling edge of the clock in the middle of the T2 or TW cycles, while /IORQ, /RD and /WR are modified on the rising edge of the clock at the start of the cycle. See the timing diagrams in the Z80 CPU User Manual for clarification. Note that if /M1 is asserted at the same time as /IORQ then this is the Z80 requesting an interrupt response vector, not a regular I/O request. Something to watch out for!
@w9gb Thank you! On the one hand the range of more advanced parts has increased, but as things have become miniaturised it can be tricky to find useful parts in DIP (especially parts like sound or video generators).
@Minifig666 Thank you very much for your comment - and happy new year to you too!
I've included some links for the dsPIC33 VDC to the description below the video. Unfortunately, it's accessed over the I²C bus.
@matchstickpro Thank you very much! Unfortunately I'd need to find some way to build custom cases; I currently buy ready-made ones and cut holes in the right places. These tend to get very expensive quickly; I did originally want to include a keyboard on this computer but couldn't find a case large enough, so went for an external one.
You may be interested in the Cambridge Z88, though, if you hadn't already seen it.
It's 128 kilobyte (1 megabit), but the Z80 only addresses the lower 64 kilobytes. The upper 64 kilobytes are not used, as there is no bank switching or similar memory management hardware in place.
I bought most of the parts from Farnell, but RS and Rapid Electronics can also be useful. For less specific parts (e.g. the passives, glue logic chips, pad board, wire, connectors etc) I used Bitsbox and Maplin.
Thats quite a nice computer you've built there. I used to be a software guy, but I got fascinated by hardware. Now I'm building my own cpu with a unique architecture out of discrete logic ICs. Perhaps I should study the architectures of these homebrew computers a bit more because I dont really have a purpose for my cpu in mind yet. Keep up the good work.
That's exactly what I'm going to implement in my BIOS, right now I'm contemplating how I'm going to use assembly to accomplish this.
I'd recommend getting to grips with Z80 assembly before building any hardware - I started by writing programs for my graphical calculator and then the Sega Game Gear. The Z80 Family CPU User Manual (um0080.pdf) is a very useful resource. Ultimately you'll need to know a fair amount about electronics and programming, and I'm not sure how much you already know. The information is nearly always in the datasheets and other reference manuals, though it can be a little dry to pick through. Good luck!
@Johceti Thank you, I enjoy working with electronics so as long as I can find the time, I'll always be working on some project or other. :-)
What a beautifull machine ! I love it
You are one brilliant young man. Congratulations with this amazing design, it's excellent. It's been a long time since I saw a good old Z80 machine. Brings a tear to the eye!
I am thinking, for educational purpose, to build several of such machines - but it would have to have a old-fashioned "operators front panel" (IMSAI 8080 or Altair style) with control switches and lots and lots of cool blinky LED's for every possible data/address signals and status monitoring. Would a design such as yours be easily adaptable to something like that?
A bit blunt to ask, perhaps, but do you have schematics, and, if so, are you willing to share or sell your design?
Thank you for posting this excellent video. I very much enjoyed it, and again my compliments with this outstanding achievement.
Thank you for your very kind comments!
A lot of the heavy lifting in this machine is done by the two microcontrollers (the ATmega644P for general I/O and the dsPIC33F to drive the display) which replaces a lot of hardware with a few lines of code. I'm not sure how that would fit in with your old-fashioned front panel idea, though the full Z80 bus is still available to drive a nice collection of blinkenlights. I imagine a front panel could be a useful (if primitive) tool to debug Z80 programs.
I'm afraid I do not have schematics and the firmware on the AVR has a handful of bugs I have not yet got around to fixing but if you contact me by email I'd be more than happy to share what I do have with you.
Thank you again!
Thank you, I hope your project comes together the way you'd like it to!
What a very cool project, i really enjoyed your video, would've loved to see one of the games you had listed, thanks for sharing this.
I downloaded the CP/M Developers Directory and read the asm files. I see what you mean about the ports now. I also looked at your other Z80 video - concerning the 2~10mhz clock change. I am sure that you know now but all you have to do is route the CS_ signal for your slow things (or them if there are more than one) through a shift register made by the proper length of flip-flops or just tap off of the appropriate lines of an actual shift register and use the resulting lengthened signal to control the Z80's wait_ input. Also - KL5C8400C from Kawasaki is Z80 compatible, comes in a 44 lead QFP, and, in a mode selectable by the state on a single pin can emulate a Z80 running at 33mhz! I think a 44-QFP to 40-pin DIP would be a drop in replacement for a Z80. And - in reference to another reader's suggestion that you use FPGA's - imho what you are doing is excellent groundwork. By going your route you will understand exactly what it is that FPGA's do when you decide to use them!
It's been years since I've even seen a Z80 computer. Thanks.
@Z80Fan Thank you, and good luck with your project! :-)
@cumesoftware Thank you very much. :-) I'd like to release more information at some point, but work has not been kind to my free time recently. Hopefully I can get back to it in the new year!
@Redhawk579 I'm sure something similar could be built, yes, though I'm more familiar with the Z80 which is why this particular machine uses a Z80.
It is a thing of beauty. I miss CP/M Over the last few years I have started to play none to seriously with Atari STs. There is some clever MS software out there that allows the ST to be connected to PC serial and parallel ports. Even though I have SD card storage devices acting as HD substitutes I like on occasion to fire up an old PC and use a serial port to save data. Alas as you say parallel and serial ports are becoming less common. Also it would be nice to do it in Linux.
@marky26uk Thank you - the games I believe you are referring to are the Zork series, which I'm not very good at and I don't think would be especially fun to watch someone else play - but if you hunt online I'm sure you can find a copy to play yourself. :-) The Z-machine that the games run on is certainly an interesting programming feat for the era.
thats just beautiful :')
I don't think so without additional (and more complicated) hardware - the AVR is not able to respond to the Z80's read/write operations quickly enough to just directly connect it to the Z80. If there was some sort of buffer between the two then it could be done, but I found it much easier to just use a flip-flop and wait states.
Getting hold of said support chips seemed to be rather difficult. I agree with you slightly more on the AVR side, but the dsPIC side would be difficult to implement on a Z80 - I can't think of any popular Z80 systems that had the Z80 generate the video signal, most were paired with a video chip of some description. Even then some classic Z80 systems would use programmable logic to implement parts of the system, so I don't think a modern microcontroller is too much of a leap.
@DYLAN102001 CP/M does not support any particular hardware configuration by default - to interact with the hardware it calls a small handful of BIOS routines, so to adapt CP/M to a particular machine all you need to do is write an appropriate BIOS. This is then linked with the BDOS using the GENCPM utility to produce a machine-specific CPM3.SYS file that is loaded into memory from disk when booting the system. Take a look at the CP/M manuals and source code for more information!
It's really amazing that stuff.
A very great work!!!!!!!!!!!!!!!!
lovely demonstration.:)
Great project and very good video!
totally blooming marvellous, how are you going to challenge yourself next ben ?
@iamgreaser I used timer 0 on the ATmega168 in fast PWM mode to produce two analogue voltages for the output of the emulated SN76489.
You could use two Z80s in a dual-core situation but I'm not sure it would be particularly efficient depending on how you organised the way they shared computer resources. I'd honestly be more inclined into looking at one of the ARM SoC platforms like a Raspberry Pi or a BeagleBoard.
Thank you - not sure I'd get on well in formal education, though, and I have little time for electronics these days unfortunately. It'd be fun to do, certainly. :-)
@ggunderscoreit Many thanks for your comments! I have tried the benchmarks in your video and posted a response.
I didnt know BBC basic allows mixing of Assembler & BASIC. Nice!
@JDepptastic I don't see why not. :-) Thanks for the comment!
Curses, I knew I had forgotten something. Thank you, and I hope you're keeping well! :-)
@themysterypie Thank you!
There's quite a lot of information to get to grips with - more than I could fit into a tutorial, certainly - but it shouldn't be too tricky, fortunately. A lot of it is down to reading the datasheets for the specific parts. For a good overview, see the book "Electronics Explained" by M.W.Brimicombe. It's quite expensive, being a textbook, so first check the preview of some of the chapters that are available on Google Books.
As far as I'm aware CP/M does not make any assumptions about port numbers or port functions - it doesn't use any I/O instructions itself, so you should be fine with address 0FFh being used like that. I assume that those are all separate functions of port 0FFh (and writing to it does not trigger all three functions in sequence) and are to be used at various stages of your boot sequence?
No Cube's Ben?!
Very impressive as always :).
@klerkbr Thanks for your kind comments!
Heh, thanks. :-) The clock at 8:00 may answer your question about whether the computer supports graphics or not.
ebay works fine for me too! :)
I have found everything I've needed so far there.
Thank you very much - I hope your project goes well too! :-)
This is great. Have you ever thought of doing a series of step by step tutorials showing how to build the computer so that a novice could follow and learn along the way? That would be brilliant.
faultelectronica Thanks! Really don't have any time for this sort of thing any more, sorry, hence the lack of new videos/projects. Would be fun but doesn't pay the mortgage... :-(
benryves i have to ask can you make it run on ms dos?
Not unless there was a Z80 version of MS-DOS. MS-DOS borrows a lot from CP/M, however, hence the two are fairly similar to use.
benryves there was it was the ZX-Spectrum Z80 v3.03 MS-DOS to be right.
As far as I can see that emulates a ZX Spectrum on a machine running DOS, rather than allow you to run DOS on a ZX Spectrum.
I'm not sure what you missed specifically but it's a cover of "Rydeen" by Yellow Magic Orchestra (also used in Sega Locomotive and Daley Thompson's Decathlon). I don't have any particularly detailed photos of the LCD but benryves dot com /journal/3622105 probably has the best example.
That sounds great to me - I was just thinking that if you were copying the OS to the start of RAM you would presumably need to copy the loader somewhere above the lower 8KB of memory first, jump to it, then swap out the BIOS, then load the OS, then reset.
@shaurz It depends how you measure "power". :-) The ATmega644P beats the Z80 as far as instructions per second goes, but has a comparatively small amount of RAM and can't run programs from RAM (so wouldn't be so useful as a general-purpose computer).
I love that mental image! Thank you for the comment. :-)
You are a good speaker!
This is fucking beautiful
@novachevyguy As one might find in a Zed Ecks Spectrum, that is!
Thank you! It could well be possible, but this is not the right sort of computer - I believe Windows 1.0 requires an PC/AT-style computer (with an x86 CPU and the other various bits of hardware that form such a computer) whereas CP/M only requires an 8080 or compatible (as long as you have enough RAM it has no other device requirements and is easy to customise for your specific hardware).
That all sounds good to me! Hope it goes together well. :-)
Sorry for the delay - I'm not sure I have any particular advice beyond getting very familiar with the Z80 Family CPU User Manual and experimenting with different designs until you find one that works nicely for your needs. What sort of computer did you have in mind, if I may ask?
If I could trouble you to make a suggestion, or more of a question or a proposition. Would you consider for your next project an actual foldable notebook with a screen, a battery, and a keyboard built in. Of course it probably wouldn't be small but hey, you could say you built the first zed 80 notebook. Just a suggestion from a fan.
Thank you and, I admire your work.
I suppose so, though I think it would be more practical to connect a tape reader to this machine via its serial port.
@freakface666666 I learned Z80 assembly by writing games for my calculator, which seems a popular route these days. Assembly gives you a good feel of how software and hardware interact. My A Level textbook, "Electronics Explained" by M.W.Brimicombe contains a basic overview of microprocessor systems, which was a good start for the hardware. I learn by doing, so experimentation is key! Good luck and please feel free to ask me any questions if you think I could help.
Very interesting. I am looking examples to understand how can i build with modern arduino or SBC's a clone of ZX spectrum 48k and Comodore 64. Well. Thanks for the video.
Ah, that looks interesting - thanks for the link! I never got flow control (in or out of band) working reliably with the AVR, which I should really reinvestigate (and which I assume would be required for such a system).
@LunaVorax Thank you very much! :-)
Thank you very much for your comment! (It's all an act, I usually have a thick Yorkshire accent).
@BinaryReader Thank you - BBC BASIC was one of the easier bits, I just downloaded it from the author's website. :-)
Bravo! Brilliant job indeed! Did you write the code for the dsPIC33 yourself or did you get it somewhere?
I've looked everywhere for an IC that cold give me VGA or composite video output and have failed to find anything, never mind in a parallel format (so I can pop it straight onto my bus). Any help would be greatly appreciated.
Thanks and happy new year.
Minifig
Very nice. I do have a few questions if you don't mind. How are you managing disk reads and writes? Is each of your disks one file on the SD card? CP/M Bios typically uses tracks and sectors.
@DYLAN102001 You'll run into problems as CP/M software is designed to run from $0100 and various vectors are stored in the zero page ($0000..$00FF). I'd suggest it would be easier to redesign your computer to be able to switch off the ROM chip once it had copied the bootloader to RAM than it would be to move CP/M and all of the software you intended to run.
I'm not sure which book you refer to but I'd personally endorse Electronics Explained by M.W. Brimicombe and The Art of Electronics by Paul Horowitz and Winfield Hill. You may wish to look them up on Google Books for previews etc before buying as they can be quite expensive!
class awesome machine!, cool vid!
I've added a link to the bottom of the description.
ooh love the sound at 9:33 - is that interference in the generated video signal or is is in the capture device? Reminiscent of every advanced military computer ever rendered by Hollywood.
+chromosundrift Haha, thanks :) The computer doesn't produce any sound itself and the capture card doesn't have sound input so I'm not sure where that noise is coming from - I used the very poor onboard audio and a cheap microphone on my desktop for that part, and judging by the 50Hz hum as well there must be some unshielded parts near the computer's video signal. I don't think I'd left Nullsoft Beep running accidentally...
Are you tying unused inputs to appropriate logic levels (high or low), including those that are connected to ATmega outputs (though those would use a pull-up/pull-down resistor)? Does your ATmega reset all other parts on the board once it has booted? (It probably should?) In my computer everything is held in a reset state until the ATmega gets around to initialising them.
Excellent.
Technically it would of course be possible (see Contiki for an example of a TCP/IP networking OS for low end 8-bit machines) but I don't think performance would be too good for the sort of large files you'd commonly be sharing via a NAS these days. Is that a project you had in mind?
I'm afraid I don't know any off the top of my head. I know Jaromir Sukuba built a computer around a PIC that emulated a Z80 and was capable of running CP/M, but that would understandably require quite a powerful PIC. For AVRs I've seen AVR-ChipBASIC - I guess you'd want something a bit like that? I don't really have any personal recommendations, sorry.
Ok, I just don't know too much about operating systems/files etc. I'm more of a hardware person and I just need a expert opinion. Writing to port 0FFH does not trigger all the functions at once, depending on what bits I write to the port I can make it do all the functions at once of one at a time. For example, if I write 00100000b to 0FFH, the reset will reset, if I write 00110000 to 0FFH, I can make it reset and give me a beep. If I write 10010000 to 0FFH, it would turn off the BIOS and beep.
Hello, you are simply a genious!
It would be interesting if you could run the "bm9" benchmark just to see the performance of BBC BASIC and the 10Mhz CPU. You may find the simple routine in my video.
SOOOO COOL!
Great design, I hope to build a simpler one one day (no screen and stuff).
The only thing is that AVR chip. Don't you thing it might be a bit cheating? I suppose it depends what you want from it, but ITS JUST GREAT!
Thank you! My intention was to build a Z80-based computer, I never had the intention of limiting myself to vintage components (other than the CPU itself). I couldn't create my own custom chips through techniques like the ULA in the ZX Spectrum, so programming a microcontroller to perform similar tasks in software doesn't seem like cheating at all to me. :)
Not to my knowledge - you would probably need to find a development board for the processor you had in mind. I imagine such a CPU would need to have a carefully-designed circuit board and would be unsuitable for use with low-tech prototyping techniques, though I have no personal experience with them.
@benryves Another question, I was looking on wikipedia about CP/M and it said that after the BIOS booted CP/M off the disk, it would sorta bank switch itself so that the operating system would start at address $0000h. Correct me if I'm wrong but is it possible to start the operating system at $2000h since my computer bios chip ( 28C64 ) does not have any sort of way to bank switch itself off?
sorry, I meant "at once OR one at a time", not "at once of one at time."
I'd like to have one of this!
Could this load gameboy games with some modification?
I'm interested in something that could play LSDJ and use native hardware, and be some kind of addon to a raspberry pi or a something on usb.
I have a question concerning what you told me a year ago. I have redesigned the computer to switch the BIOS on and off the first 8kB of the 64kB Z80 ram space.
By writing to port 0FFh, I can switch on and off the BIOS chip, reset the entire computer, and produce a 1 sec. speaker beep. Will I have any problems with port 0FFh being used in this way?