HI Adrian, I have a Plexus 25 engineering manual that includes schematics and all sorts of technical information on that system. The P25 (from 1982) is a low end previous model of your P20 (1985) so, there is a high chance that the underlying hardware architecture would be similar enough to propel you towards the right path into a fully working hardware system. I also have both your P20 and the P25 sale brochures which seem to back up my claims. I also have a user manual for the P40. Let me know if you need them, and I can email you the corresponding digitalized documents to some address you provide me with.
@@Toonrick12 With Bitsavers, while it is great, when you send them anything it's theirs to do whatever they want to get it up and available. Even if that means disassembling the documents. Unless things have changed Bitsavers will not return any documents you sent to them.
@@Toonrick12 The Internet Archive has a mirror of the Bitsavers documents. At the main search prompt (not the Wayback Machine prompt), enter "Bitsavers Plexus" and leave "Search metadata" selected... bingo! As I noted on the last video, various earlier Plexus machines like the P/25 are Z8000-based. That doesn't mean that there won't be design similarities, and some of the 68000-based models apparently use the Z8000 as a peripheral chip, but at some point the architectural differences will have caused the designs to have diverged.
Hi, my friend and I had a ton of Plexus machines; P/35's, P/40, P/60's, P/75, P/90 and and P/95's. I also had the complete Plexus tape library of over 5000 mag and cartridge tapes. I had a DEC TU/45 tape deck on my P/75 with the Pertec interface. Also had a Kennedy mag tape drive and eventually, we ended up with 2 Telex (can't remember the model) drives that were 800/1600/6250. We also had tons of manuals. I gave the P/75 to the Diablo Valley College back in the late 80's and the P/90 went to the Computer History Museum. We traded and sold a bunch of P/60's to an outfit in Colorado for cash and the 2 P/95's. My buddy Al, played around upgrading the P/60 from 12.5Mhz to 24.5. Couldn't get to 25. I had the source tapes for Unix SVR5.2, 5.3 and ended up porting 5.3 to my P/95. All I got left is a box of Plexus key fobs, LOL. Fun times, but I started on Linux in 1990 and been with the ever since.
For a long time I've thought that if a person is truly an expert in something, like, really knowledgeable and accomplished, and also enthusiastic, then it doesn't matter what that thing is: listening to them talk about it is a joy. You're proof of this, Adrian, because I don't know the first thing about any of this stuff you're doing, but it's great fun to watch you do it.
Not only does this system sound like an old diesel, the key switch needs to be in the "Start" position to warm up the glow plugs for a few seconds before going to "Run". 🙂
@@rawr51919 Both my old VW diesel Rabbit, and Volvo diesel had a standard key switch. You turned it to the on position. A glow plug light would turn on. When the light extinguished, you could start the car. The car would turn over without doing the glow pug routine, but it most likely wouldn't start with the available battery.
Really loving this series. I have been in the oil and gas industry all my life. In my 20’s I was a unix admin for Sun and SGI for a US energy contractor. I had such fun playing with the hardware, reinstalling OS adding memory. It brought back so many great memories. Thank you. It’s unfortunate how they were ditched for PC architecture almost over night. However, for at least a few years we all had an old Sun or SGI box sitting under our desks switched off just in case we had to revert. All the best Alex.
It is a cliff hanger Adrien!!!.............. I didn't even know I cared about this server until I got hooked into watching it. Please hurry and do part 3.
Rare or niche computers are my favorite. So much effort and time went into machines like this, only to be almost completely forgotten, just for us to look at it 40 years later with fascination.
At 53:57, where the boot commands which reside in the boot ROM is dumped, we can see that these commands look very Unix like, but my guess is they are actually not true Unix commands, in the sense that they are running natively without an operating system, (which has a separate user space and kernel space dividing hardware access privileges). They look to be available commands to diagnose the file system, do formatting and repairs to the file system ("format.pt" and "fsck.pt"), prior to booting Unix SysV. The names of the command seem to have the device extension, i.e. "mkfs.pt" for primary tape. This either indicates which device the mkfs ("make file system") command applies to, or perhaps, which device the command needs to execute from. The full specification (e.g "mkfs.pt(,4)") could be referring to a priority level, or the SCSI bus id, but id's above 7 don't make sense, unless the value applies to two different SCSI busses?. Typing the full command with the extension may be required, i.e. "unix.pt(,2)" or "sys5.pt(,2)" are likely the commands to begin booting Unix, from tape. I would try typing "help.pt" and "help.pt(,)" to see if anything executes differently to "help"? Obviously exercise caution running "mkfs.pt(,4)", "dd.pt(,13)", "format.pt(,3)" as they can modify the device. Try "ls.pt(,14)" once the drive is connected? Also, try "help.pd" and "help.pd(,)" to refer to the disk drive? Just some Unixen oriented suggestions, no actual experience with Plexus machines.
At 3:30 I just wanted to add the little nugget that on the power supply is the TÜV logo with written above and beyond "BAUART GEPRÜFT". The TÜV (Technischer Überwachungs Verein) is the German organisation for checking safety. And this mark says that it got approved so can be sold in Germany. History side note, the TÜV was founded in the 19th century and started for checking safety of steam machines as there were too many accidents and resulting death in that time from explosions.
Yeah, you have to have the multibus terminator card in the correct place (and have a stable card - check all the resistors :-) ), or the basic multibus hardware test will fail, and the bootstrap process will report a fault.
Thanks for making these great videos. I have a PiDP-11 which comes with a number of vintage UNIX systems. One is System Vr1. I wanted to see a preview of what you might see once you get the real thing working. One thing I found is that the file system is quite fragile if you don't power it down correctly. Had to run the fsck program a lot. Have been compiling the Dhrystone benchmark to check performance.
You should look into getting some RJ45 to DE-9 and DB-25 adapters for the next time you need to make a custom RS232 cable. Not only can you use them with long Ethernet cables to run across your lab, the connectors come with the backshells open and without the pins placed in the connector so you can customize the pin mapping as needed. Since they're standard D-sub crimp pins, you can use a pin removal tool to swap pins if your first try wasn't correct or if you want to recycle them between projects.
This is prevalent in some industrial settings. Usually RS485/422 though. One buddy of mine fried his laptop Ethernet port due to assuming that RJ45 must be Ethernet.
@@yt45204 In broadcast studios the sat receivers still use DB9 for audio and usually DB37 for GPIO. The screw terminal connectors has saved me so so much work not having to break out a soldering iron every time something needs to be changed.
Cat-5 cable is not shielded. Haven't seen anyone use the removable pin dsub connectors except in aerospace or prototyping for at least 30 years. I doubt the commercial amazon quality available today will retain the pins pins or keep them straight.
My experiance with those old systems using serial comm ports is that a comm port gets active when you press the enter key, to signal the Serial IO processor that a serial port is connected to a live terminal and it can eventual calculate the connection settings (like speed) the connected terminal is using.
It's a sad indictment of TV nowadays that I'd rather watch someone for an hour diagnose a computer that has no practical application than any of the dross thats on.
My primary TV channel IS RUclips.. And then whatever Star Wars or Star Trek is on. Currently on Reality TV.. Farmer wants a wife. Young farmer looking for romance is presented with a bevey of beauties who have never seen a dung heap. Hilarity evolves when they realise they will have to give up city life for the country.. and No Mabel - you cannot be a fly-in fly-out wife.😊
I am still not entirely sure why the hard drive is not being connected, preferably with the MFM emulator, as the commands require an OS to be loaded... is not making a lot of sense to me but I may be missing something...
At 51:34 the documentation mentions just pressing Return at the colon prompt and it should respond with some system info. I couldn’t tell in the video if you tried this.
Really enjoying this mini series and looking forward to the next chapter. So crazy that this machine existed and was used but has never been documented. You are doing incredible work.
Adrian I have multiple machines with that tape drive exact model that I’ve restored successfully. I’ve even replaced the bands that snap on the tapes. Terrys Rubber Wheels will restore the capstan that needs replacement. I’ve done so many it’s easy for me. I’ve also replaced one cap on it that’s electrolytic.
Good to know -- unfortunately without the system restore tape, there is little that can be done with this drive other than back-up the system. (And I don't really need to since I have the drive emulator anyways)
I wonder: there must be at least a couple hundred machines that were sold. Is there anyone who worked at Plexus who might know either a) if there are still tapes somewhere or b) customers where there might be leads and maybe people who grabbed tapes or machines as they were being phased out?
@@root42 I have quite a large collection of Altos Servers, this Plexus looks a lot like the Altos series 2000 in a lot of ways. A lot of the 80386 2000 series used tapes for installation and backup. The Altos 386 machines ran SCO System V Unix. I unfortunately do not have any series 2000 but sometimes they came with one 5 1/4 disk and the tape for install. As far as I know the Altos machines were only intel based (I could be wrong). Altos had the OS license and sort of created their own customized installation of these OS's. I am not sure if Plexus did this as well. You might get away if your drive image doesn't work being able to install SCO Unix System V. I have probably a dozen of David G's drive emulator boards and use them on all my MFM machines.
The TAO of Comms Keep in mind the Four Noble Truths: 1. Comms is constant suffering. 2. This suffering is caused by craving. The lust for reliable high-speed comms deflects the soul from Nirvana. 3. The cessation of suffering is not possible. 4. There is no fourth Noble Truth. Some ask whether two comms systems can ever be identical. The true sage knows that even one comms system can never be identical. If a comms problem seems too difficult to solve, stop. Clear your mind and reflect a while in quiet meditation. You will then realize that your original perception of difficulty was in fact a gross underestimate. All comms problems can be solved by the application of one of the two great techniques: A. Random trial and error B. Methodical trial and error Remember the Eightfold Path to connection: * Male, 9-way, DCE * Female, 9-way, DCE * Male, 25-way, DCE * Female, 25-way, DCE * Male, 9-way, DTE * Female, 9-way, DTE * Male, 25-way, DTE * Female, 25-way, DTE
That's the cliff hanger of the century! Great trouble shooting, can't wait for the next part. It sounds like the boot ROM could load external commands from a tape or a disk and acts pretty similar to a shell, so once you have a disk connected, you may have much more success. That would allow to ship new tapes for command fixes instead of new EPROMs.
I love those old Malllory caps--I probably would have made the same mistake in overlooking the physical issue because they're normally so damn reliable.
@@adriansdigitalbasement Not sure the Mallory caps are OK, they all measured well above the rated capacitance. Which could be OK given how loose most capacitors are spec'd but measuring too high capacitance also THE classic sign that a capacitor is leaking. This happens because they measure capacitance by how long it takes to charge to a certain level and if the capacitor leaks this obviously takes longer which gives an inflated value. The meter you used didn't seem to have a leakage number so I'd recommend checking them for leakage before reusing.
@@Torbjorn.Lindgren You're not correct on this - when they leak, the electrolyte is limiting the electrical contacts up to the plates and you LOSE capacitance. The measuring device Adrian was using detects resistance as well so it could not be confused by high ESR. It is normal for electrolytic caps to start 50% over their rated capacitance and tolerance is often +80/-20%.
3:18 The marking "BAUART GEPRÜFT TÜV" means that the German TÜV Süd (Technischer Überwachungsverein Süd, lit.: Technical Supervisory Club South" has performed periodic on-site checks at the manufacture to ensure that the product is safe for its intended use.
@@captainchaos3667a) because the certification has value outside of Germany (in fact TÜV exists even in China) b) because it has particular values if you want to sell in Germany
Geman here: No, "Bauart geprüft" does not mean TÜV does any kind of manufacturing process inspection. It's just the German translation of "type approved", so they approved that specification and possibly a sample product shipped to TÜV conform to regulations. It's basically the German equivalent of a "UL listed equipment" or "UL recognized component" mark.
Hey, Adrian...see you at VCFSW! And lots of people are comparing your video on this machine to "Forgotten Machines"...so I love the crossover! Thank you!
@28:10 Be careful using both the multimeter and the scope function at once, I am pretty sure the shield from the scope probe is connected to the common input of the multimeter, you could short something out.
I have a Hercus CNC lathe with an ANCA controller and the 25 pin serial port is 5 levels of messed up. Many people have issues communicating with these boards (to the point that some say it can't be done) but once you figure out what it is doing it works perfectly. So you are probably 100% correct with what you have discovered with the serial port. Thanks Adrian.
You mentioned you don't have the multibus card cage installed. It had a board with a ton of resistors, no? They might be necessary for the power supplies to be happy.
Or just the self-test... Those are probably termination resistors. The bus may have floating voltage levels across it, confusing the self-tests, giving varying and inconsistent results.
I get the feeling that the spring loaded key switch may be critical for the power supply correctly powering up the main board. Breaking the lock may have messed that up.
@@adriansdigitalbasement wishful thinking I guess... Hopefully you'll get it sorted enough to see first person how primitive UNIX was in the mid 80s... no swap space... everything statically linked... I think vi was just around a year or two before 85
I believe MultiBus requires some amount of load as well as termination. Get the secondary supply working with the MultiBus cage attached before you try the hard disk (real or emulated), I bet it’ll fix the MultiBus diagnostic warning in the self test.
Actually, I’m almost certain MultiBus requires termination, so you’ll either need the terminator board or the card cage with terminator board installed.
RUclips's algorithms recommended this to me. How fun, this took me back decades into the world of microelectronics. I love your DMM with build-in scope! Who would have thought that 🫨. I sure recognize your reaction when things first start to work 😃👍. Thanks for posting!
On the last video I commented that the disk might have an ancient UNIX disklabel, but judging by what was in that manual, there's no disklabel, just one bare filesystem.
This is the most relaxing content to watch relating to old and extremely rare machines. I played around with various UNIX on VM and HP UX on an old Itanium server. But to see an old UNIX machine running on its organic components from the 80’s is so cool! You have a real talent for machines and a good way of explaining how it all works.
I wonder if the multiple “PLEXUS” resets near the end of the video are just caused by switch bounce when switching from reset to run. Might not be an issue if the intended spring action was working.
Seeing that Archive QIC is a blast from the past. I worked for the main competitor and they made a similar drive. I remember that sound they made - used to hear it walking through our QC department whilst they went through burn-in. One model did end up in the IBM PC-RT. I didn’t work on that project but a coworker did. IBM was always so super-secretive about everything. Like they were CIA agents or similar!
Look, I don't know how I got here, or why I have been captivated by some giganto unix box from the 80's, but I'm going to need to see the rest of this NOW!.
The DB9 serial connections are using software flow control Xon Xoff, those are the user interfaces. The DB25 is the supervisor control port ie the Command port
You may well find that the ':' prompt will have no commands at all, or might accept single character commands; anything longer is a filename. Some of the older Unix machines I used to manage in the 90s were like that (although were late 80s rather than mid 80s). It doesn't seem to apply here, but some Unix machines could take a _long_ time to get through basic (or advanced) diagnostics. I was chatting to a Sun engineer whilst waiting for an E450 (? it might have been one of the other ones - it was a long time ago) to silently finish testing all its memory and he told me about an E10000 that he was running full diagnostics on which took 8 hours to get through the diagnostics. Not that waiting 8 hours is a serious suggestion, but 5 minutes might be better than 30s. Serial ports are funny things even ignoring all the wiring issues. 9600 baud is a good speed to start with (at least for 1980s and later) and banging the return key to wake up a serial port isn't unusual although a system console tends to be different.
I’m tearing my hair out over here! The error messages are literally saying that the card and disk are not found! The card and disk are on the bench, not installed in the system. Grrrr
At this point it is looking for whatever you type on disk or tape. You just have to give it something to boot from, either the kernel or a utility program. The boot PROM fully understands the UNIX file system, think of it as GRUB in ROM.
You can test whether you need a null modem by measuring which pin is the TX on a piece of equipment. That pin will be driven with whatever positive voltage is used. This works regardless of logic level outputs (1.8-5V) or RS-232 levels (8-15V).
Those Rifa XT polyester caps shown next to the mains connector on the seond power supply board will be part of a common-mode mains filter. And it is a good idea to replace them with polyproylene caps. Metallized polyester caps are unreliable when used like that.
As I know 9 pin usually for console or dumb terminal and they use XON/XOFF software flow control, printer or hardware 25 pin will have RTS/DTS hardware flow control.
"Lights are not in the rebooting way but in the i should be working way" I absolutely gonna steal that hehehehe, man i like your videos so much! okay keep watching, just feel the need to broadcast that xD
Hi Adrian, good to see some positive signs of life on that mini computer :) I could see myself falling for the same trap you did with those "loose" Mallory caps 😂 - Enjoyed your reaction to the "blinkenlights", too! - Hopefully, someone watching can provide or point you at copies of the technical, service and user doco for that model of Plexus ... - You've already alluded to two places where you expect to have to check and in one case enter values: - PROM on one the HDD subsystem boards - Battery-backed RAM on the motherboard - Will be _very_ interesting to see the results of hooking the MFM emulator up to the interposer, assuming the BIOS will let you get as far as attempting booting from HDD 🍻
Can you put a heatsink on the large resistor that discolored the PCB in the large power supply? Given that the large PSU has active cooling I think it would make a big difference going forward.
HI Adrian, I have a Plexus 25 engineering manual that includes schematics and all sorts of technical information on that system. The P25 (from 1982) is a low end previous model of your P20 (1985) so, there is a high chance that the underlying hardware architecture would be similar enough to propel you towards the right path into a fully working hardware system. I also have both your P20 and the P25 sale brochures which seem to back up my claims. I also have a user manual for the P40. Let me know if you need them, and I can email you the corresponding digitalized documents to some address you provide me with.
I was going to say that Bitsavers would love to have those documents, but they already have them
To be honest, it would be a better idea to upload the documents to the Internet Archive. That way more people can have access to them.
@@Toonrick12 With Bitsavers, while it is great, when you send them anything it's theirs to do whatever they want to get it up and available. Even if that means disassembling the documents. Unless things have changed Bitsavers will not return any documents you sent to them.
Bitsavers already has the P/25 Engineering manual online: 5018-1A_P25_EngineeringManual_Jun82.pdf
@@Toonrick12 The Internet Archive has a mirror of the Bitsavers documents. At the main search prompt (not the Wayback Machine prompt), enter "Bitsavers Plexus" and leave "Search metadata" selected... bingo!
As I noted on the last video, various earlier Plexus machines like the P/25 are Z8000-based. That doesn't mean that there won't be design similarities, and some of the 68000-based models apparently use the Z8000 as a peripheral chip, but at some point the architectural differences will have caused the designs to have diverged.
Hi, my friend and I had a ton of Plexus machines; P/35's, P/40, P/60's, P/75, P/90 and and P/95's. I also had the complete Plexus tape library of over 5000 mag and cartridge tapes. I had a DEC TU/45 tape deck on my P/75 with the Pertec interface. Also had a Kennedy mag tape drive and eventually, we ended up with 2 Telex (can't remember the model) drives that were 800/1600/6250. We also had tons of manuals. I gave the P/75 to the Diablo Valley College back in the late 80's and the P/90 went to the Computer History Museum. We traded and sold a bunch of P/60's to an outfit in Colorado for cash and the 2 P/95's. My buddy Al, played around upgrading the P/60 from 12.5Mhz to 24.5. Couldn't get to 25. I had the source tapes for Unix SVR5.2, 5.3 and ended up porting 5.3 to my P/95. All I got left is a box of Plexus key fobs, LOL. Fun times, but I started on Linux in 1990 and been with the ever since.
For a long time I've thought that if a person is truly an expert in something, like, really knowledgeable and accomplished, and also enthusiastic, then it doesn't matter what that thing is: listening to them talk about it is a joy. You're proof of this, Adrian, because I don't know the first thing about any of this stuff you're doing, but it's great fun to watch you do it.
Well said.
Being a massive UNIX geek and an m68K fan, plus a UNIX system I've never heard of, this series is ticking a huge number of boxes for me. Thanks Adrian
I'm dreaming of teletypes 🙂
Not only does this system sound like an old diesel, the key switch needs to be in the "Start" position to warm up the glow plugs for a few seconds before going to "Run". 🙂
Other way round, run activates glow plugs, start runs the starter
You got it bang on otherwise :)
@@rawr51919 Both my old VW diesel Rabbit, and Volvo diesel had a standard key switch. You turned it to the on position. A glow plug light would turn on. When the light extinguished, you could start the car. The car would turn over without doing the glow pug routine, but it most likely wouldn't start with the available battery.
Jody! the places I run into you 😂
@@tedw7193 lol - yes, we overlap channels quite a bit. 🙂
So it’s like starting up my grandpa’s old John Deere when I was a kid, but with slightly less hand cranking 😂
Really loving this series. I have been in the oil and gas industry all my life. In my 20’s I was a unix admin for Sun and SGI for a US energy contractor. I had such fun playing with the hardware, reinstalling OS adding memory. It brought back so many great memories. Thank you. It’s unfortunate how they were ditched for PC architecture almost over night. However, for at least a few years we all had an old Sun or SGI box sitting under our desks switched off just in case we had to revert. All the best Alex.
It is a cliff hanger Adrien!!!.............. I didn't even know I cared about this server until I got hooked into watching it. Please hurry and do part 3.
Adrian.
@@jinxterx thanks Jinxrarx! cheers
@@moogfooger You're welcome moofbooger! :D
@@jinxterx Mr Terx, don't you know how to spell? :->?!!!"...---...
@@moogfooger No, you can teech me???
As much as I enjoy the higher-volume micros, there's something I find fascinating about these seemingly very well-built professional machines.
Rare or niche computers are my favorite. So much effort and time went into machines like this, only to be almost completely forgotten, just for us to look at it 40 years later with fascination.
The insides of sun servers where art, still love the design of the v240, v440 series
I've been screaming at the screen for the last half hour "JUST PLUG IN THE HARD DRIVE!!!!!!!!!!!!!!!!!!!!!!" We might not be alive in another week.
and the secondary power supply!!
Firmware: multibus failed
Me, at the screen: PLUG IN THE MULTIBUS CAGE AND TERMINATOR BOARD!!!
Consider me entertained! :D
username does check up.
@@44Bigsfair point
Yeah you are milking it a bit too hard. Plug in the HDD pls
At 53:57, where the boot commands which reside in the boot ROM is dumped, we can see that these commands look very Unix like, but my guess is they are actually not true Unix commands, in the sense that they are running natively without an operating system, (which has a separate user space and kernel space dividing hardware access privileges). They look to be available commands to diagnose the file system, do formatting and repairs to the file system ("format.pt" and "fsck.pt"), prior to booting Unix SysV. The names of the command seem to have the device extension, i.e. "mkfs.pt" for primary tape. This either indicates which device the mkfs ("make file system") command applies to, or perhaps, which device the command needs to execute from. The full specification (e.g "mkfs.pt(,4)") could be referring to a priority level, or the SCSI bus id, but id's above 7 don't make sense, unless the value applies to two different SCSI busses?. Typing the full command with the extension may be required, i.e. "unix.pt(,2)" or "sys5.pt(,2)" are likely the commands to begin booting Unix, from tape. I would try typing "help.pt" and "help.pt(,)" to see if anything executes differently to "help"? Obviously exercise caution running "mkfs.pt(,4)", "dd.pt(,13)", "format.pt(,3)" as they can modify the device. Try "ls.pt(,14)" once the drive is connected? Also, try "help.pd" and "help.pd(,)" to refer to the disk drive? Just some Unixen oriented suggestions, no actual experience with Plexus machines.
03:48 Interesting the German sticker from TÜV Reinland - type tested.
At 3:30 I just wanted to add the little nugget that on the power supply is the TÜV logo with written above and beyond "BAUART GEPRÜFT".
The TÜV (Technischer Überwachungs Verein) is the German organisation for checking safety. And this mark says that it got approved so can be sold in Germany.
History side note, the TÜV was founded in the 19th century and started for checking safety of steam machines as there were too many accidents and resulting death in that time from explosions.
This is bringing so many things up that I hadn't thought about in nearly 40 years...
Yeah, you have to have the multibus terminator card in the correct place (and have a stable card - check all the resistors :-) ), or the basic multibus hardware test will fail, and the bootstrap process will report a fault.
Adrian's Saturday videos are the highlight of my tech RUclips week. Thanks Adrian!
I think this might be my favourite video of yours yet! What a journey! 🤩
Thanks for making these great videos. I have a PiDP-11 which comes with a number of vintage UNIX systems. One is System Vr1. I wanted to see a preview of what you might see once you get the real thing working. One thing I found is that the file system is quite fragile if you don't power it down correctly. Had to run the fsck program a lot. Have been compiling the Dhrystone benchmark to check performance.
oh no! a cliffhanger! can't wait to see it boot Unix
I'm rooting for you Adrian! I want to see this thing running in all its glory. See you at VCFSW!
I like when you creating such long videos, this is better that all the discovery channels, and watch it even when sleeping
You should look into getting some RJ45 to DE-9 and DB-25 adapters for the next time you need to make a custom RS232 cable. Not only can you use them with long Ethernet cables to run across your lab, the connectors come with the backshells open and without the pins placed in the connector so you can customize the pin mapping as needed. Since they're standard D-sub crimp pins, you can use a pin removal tool to swap pins if your first try wasn't correct or if you want to recycle them between projects.
Good idea. There are also DB9/DB25s with screw terminals for quick changes
Adrian and clabretro collab when?
This is prevalent in some industrial settings. Usually RS485/422 though. One buddy of mine fried his laptop Ethernet port due to assuming that RJ45 must be Ethernet.
@@yt45204 In broadcast studios the sat receivers still use DB9 for audio and usually DB37 for GPIO. The screw terminal connectors has saved me so so much work not having to break out a soldering iron every time something needs to be changed.
Cat-5 cable is not shielded. Haven't seen anyone use the removable pin dsub connectors except in aerospace or prototyping for at least 30 years. I doubt the commercial amazon quality available today will retain the pins pins or keep them straight.
Nice to see some signs of life, looking forward to part 3!
My experiance with those old systems using serial comm ports is that a comm port gets active when you press the enter key, to signal the Serial IO processor that a serial port is connected to a live terminal and it can eventual calculate the connection settings (like speed) the connected terminal is using.
It's a sad indictment of TV nowadays that I'd rather watch someone for an hour diagnose a computer that has no practical application than any of the dross thats on.
I spend time watching guys power wash cars now. Haven't turned on the "TV" over two years.
My primary TV channel IS RUclips..
And then whatever Star Wars or Star Trek is on.
Currently on Reality TV.. Farmer wants a wife. Young farmer looking for romance is presented with a bevey of beauties who have never seen a dung heap. Hilarity evolves when they realise they will have to give up city life for the country.. and No Mabel - you cannot be a fly-in fly-out wife.😊
I think the last time the tv was on was for the superbowl, and before that was the superbowl before.
I am still not entirely sure why the hard drive is not being connected, preferably with the MFM emulator, as the commands require an OS to be loaded... is not making a lot of sense to me but I may be missing something...
At 51:34 the documentation mentions just pressing Return at the colon prompt and it should respond with some system info. I couldn’t tell in the video if you tried this.
Really enjoying this mini series and looking forward to the next chapter. So crazy that this machine existed and was used but has never been documented. You are doing incredible work.
I'd just fix those larger Mallory caps, seems to have enough material on there to solder some wire to.
Adrian I have multiple machines with that tape drive exact model that I’ve restored successfully. I’ve even replaced the bands that snap on the tapes. Terrys Rubber Wheels will restore the capstan that needs replacement. I’ve done so many it’s easy for me. I’ve also replaced one cap on it that’s electrolytic.
Good to know -- unfortunately without the system restore tape, there is little that can be done with this drive other than back-up the system. (And I don't really need to since I have the drive emulator anyways)
I wonder: there must be at least a couple hundred machines that were sold. Is there anyone who worked at Plexus who might know either a) if there are still tapes somewhere or b) customers where there might be leads and maybe people who grabbed tapes or machines as they were being phased out?
@@root42 I have quite a large collection of Altos Servers, this Plexus looks a lot like the Altos series 2000 in a lot of ways. A lot of the 80386 2000 series used tapes for installation and backup. The Altos 386 machines ran SCO System V Unix. I unfortunately do not have any series 2000 but sometimes they came with one 5 1/4 disk and the tape for install. As far as I know the Altos machines were only intel based (I could be wrong). Altos had the OS license and sort of created their own customized installation of these OS's. I am not sure if Plexus did this as well. You might get away if your drive image doesn't work being able to install SCO Unix System V. I have probably a dozen of David G's drive emulator boards and use them on all my MFM machines.
The TAO of Comms
Keep in mind the Four Noble Truths:
1. Comms is constant suffering.
2. This suffering is caused by craving. The lust for reliable high-speed comms deflects the soul from Nirvana.
3. The cessation of suffering is not possible.
4. There is no fourth Noble Truth.
Some ask whether two comms systems can ever be identical. The true sage knows that even one comms system can never be identical.
If a comms problem seems too difficult to solve, stop. Clear your mind and reflect a while in quiet meditation. You will then realize that your original perception of difficulty was in fact a gross underestimate.
All comms problems can be solved by the application of one of the two great techniques:
A. Random trial and error
B. Methodical trial and error
Remember the Eightfold Path to connection:
* Male, 9-way, DCE
* Female, 9-way, DCE
* Male, 25-way, DCE
* Female, 25-way, DCE
* Male, 9-way, DTE
* Female, 9-way, DTE
* Male, 25-way, DTE
* Female, 25-way, DTE
First time anyone has complained that a noctua fan is too quiet
My thoughts exactly
That's the cliff hanger of the century! Great trouble shooting, can't wait for the next part. It sounds like the boot ROM could load external commands from a tape or a disk and acts pretty similar to a shell, so once you have a disk connected, you may have much more success. That would allow to ship new tapes for command fixes instead of new EPROMs.
I actually skipped a heartbeat when he just typed "mkfs" ;-)
I love those old Malllory caps--I probably would have made the same mistake in overlooking the physical issue because they're normally so damn reliable.
Yeah I just figured they wobbled because they left excessive leads above the PCB.... and yeah, the most rock solid old caps ever it seems like!
@@adriansdigitalbasement Not sure the Mallory caps are OK, they all measured well above the rated capacitance. Which could be OK given how loose most capacitors are spec'd but measuring too high capacitance also THE classic sign that a capacitor is leaking. This happens because they measure capacitance by how long it takes to charge to a certain level and if the capacitor leaks this obviously takes longer which gives an inflated value. The meter you used didn't seem to have a leakage number so I'd recommend checking them for leakage before reusing.
@@Torbjorn.Lindgren You're not correct on this - when they leak, the electrolyte is limiting the electrical contacts up to the plates and you LOSE capacitance. The measuring device Adrian was using detects resistance as well so it could not be confused by high ESR. It is normal for electrolytic caps to start 50% over their rated capacitance and tolerance is often +80/-20%.
@@adriansdigitalbasement I would add 'pigtails' to those caps and save them for a future project.
The wobbling bothered me from the beginning. They're not supposed to do that.
40:13 - love to see how this fan directly compared on a test compared to a noctua
Great series! Thanks! Looking forward to the MFM boot!
3:18 The marking "BAUART GEPRÜFT TÜV" means that the German TÜV Süd (Technischer Überwachungsverein Süd, lit.: Technical Supervisory Club South" has performed periodic on-site checks at the manufacture to ensure that the product is safe for its intended use.
exactly, the TÜV also approves cars, locomotives and power plants...
Why would that be in a Californian computer?
@@captainchaos3667a) because the certification has value outside of Germany (in fact TÜV exists even in China) b) because it has particular values if you want to sell in Germany
@@captainchaos3667 The certification is voluntary, so I can only surmise that Plexus did this by default for distribution on a European market.
Geman here: No, "Bauart geprüft" does not mean TÜV does any kind of manufacturing process inspection. It's just the German translation of "type approved", so they approved that specification and possibly a sample product shipped to TÜV conform to regulations. It's basically the German equivalent of a "UL listed equipment" or "UL recognized component" mark.
Hey, Adrian...see you at VCFSW!
And lots of people are comparing your video on this machine to "Forgotten Machines"...so I love the crossover! Thank you!
I haven't anticipated a part 3 to something this much, since Return of the Jedi!
I just hope it isn't as disappointing.
Looking at this mother board at 26:30, I think VLSI chips are a good thing after all.
Wonderful diagnosis of a 'headless' UNIX (R) machine trying to work out if it is alive.
@28:10 Be careful using both the multimeter and the scope function at once, I am pretty sure the shield from the scope probe is connected to the common input of the multimeter, you could short something out.
Hello Adrian this project is very exciting and I can't wait to see part 3 !
27:32, I can't stop LOL'ing..."Blinky blinky, blinky blinky". We are so much alike lmao.
Great video. I love watching you troubleshoot unique systems.
uniques
That machine is so fascinating! Can't wait for the next part.
This series brought me to your channel! Fantastic stuff.
I have a Hercus CNC lathe with an ANCA controller and the 25 pin serial port is 5 levels of messed up. Many people have issues communicating with these boards (to the point that some say it can't be done) but once you figure out what it is doing it works perfectly.
So you are probably 100% correct with what you have discovered with the serial port.
Thanks Adrian.
Hmp! It has a few blinky LEDs but by far not enough :-)
Exited to see the next episode! Brings back memories, this little beast.
Oh I'm so enjoying the journey. And the cliffhanger is perfect. Good fortune with this.
Solder new leads on those perfectly good capacitors!
Cliff Hanger!!!!! Well done Adrian. Enjoying it heaps.
The highlight of the whole video, worthy of a clip of its own is 27:28. Blinky-blinky !!!
You mentioned you don't have the multibus card cage installed. It had a board with a ton of resistors, no? They might be necessary for the power supplies to be happy.
Or just the self-test... Those are probably termination resistors. The bus may have floating voltage levels across it, confusing the self-tests, giving varying and inconsistent results.
27:02 - LOL, it was like you turned on an old cranky tractor with those sounds :D
Sounds like a TK50 on power up. Old linear tape drives made those grunty noises when zeroing the head positioner.
Bravo. That's real archaeology. Keep going, mate. :)
I get the feeling that the spring loaded key switch may be critical for the power supply correctly powering up the main board. Breaking the lock may have messed that up.
Luckily this was not the case, I've already completely reversed engineered that whole circuit :-)
@@adriansdigitalbasement wishful thinking I guess... Hopefully you'll get it sorted enough to see first person how primitive UNIX was in the mid 80s... no swap space... everything statically linked... I think vi was just around a year or two before 85
Bits don't care about your feelings.
This has been such a great ride so far! I cannot wait for the next video.
I believe MultiBus requires some amount of load as well as termination. Get the secondary supply working with the MultiBus cage attached before you try the hard disk (real or emulated), I bet it’ll fix the MultiBus diagnostic warning in the self test.
Actually, I’m almost certain MultiBus requires termination, so you’ll either need the terminator board or the card cage with terminator board installed.
Really enjoying this series! M68k + UNIX is sweet.
"So, were getting the good LEDs, there. The green one's on, plus one of the other ones." 27:08
This cracked me up, for whatever reason. lol
This was a great video. I hope so much you get this beautiful machine running its OS without a boot tape.
RUclips's algorithms recommended this to me. How fun, this took me back decades into the world of microelectronics. I love your DMM with build-in scope! Who would have thought that 🫨. I sure recognize your reaction when things first start to work 😃👍. Thanks for posting!
On the last video I commented that the disk might have an ancient UNIX disklabel, but judging by what was in that manual, there's no disklabel, just one bare filesystem.
This was an awesome video! Looking forward to next week.
I'm 100% invested in seeing what happens next.
This is the most relaxing content to watch relating to old and extremely rare machines. I played around with various UNIX on VM and HP UX on an old Itanium server. But to see an old UNIX machine running on its organic components from the 80’s is so cool! You have a real talent for machines and a good way of explaining how it all works.
Adrian - could you send a bunch of old RIFAs to the SlowMo guys to show what happens when they blow? ? Might be spectacular, and a channel crossover.
Thank you Adrian excellent video. Cheers
I wonder if the multiple “PLEXUS” resets near the end of the video are just caused by switch bounce when switching from reset to run. Might not be an issue if the intended spring action was working.
Seeing that Archive QIC is a blast from the past. I worked for the main competitor and they made a similar drive. I remember that sound they made - used to hear it walking through our QC department whilst they went through burn-in. One model did end up in the IBM PC-RT. I didn’t work on that project but a coworker did. IBM was always so super-secretive about everything. Like they were CIA agents or similar!
Look, I don't know how I got here, or why I have been captivated by some giganto unix box from the 80's, but I'm going to need to see the rest of this NOW!.
RS 232 Mc1488. & 89. Going back in time for me when I was in IT at a local newspaper starting in 79
Noctua are high end fans for gaming and such. Excellent airflow with minimal noise, so you probably don't need to worry about the airflow.
...loving this....better than any Netflix mini series
The DB9 serial connections are using software flow control Xon Xoff, those are the user interfaces. The DB25 is the supervisor control port ie the Command port
The Plexus knows what you're up to during your stress breaks.
Rubout encountered.
You may well find that the ':' prompt will have no commands at all, or might accept single character commands; anything longer is a filename. Some of the older Unix machines I used to manage in the 90s were like that (although were late 80s rather than mid 80s).
It doesn't seem to apply here, but some Unix machines could take a _long_ time to get through basic (or advanced) diagnostics. I was chatting to a Sun engineer whilst waiting for an E450 (? it might have been one of the other ones - it was a long time ago) to silently finish testing all its memory and he told me about an E10000 that he was running full diagnostics on which took 8 hours to get through the diagnostics. Not that waiting 8 hours is a serious suggestion, but 5 minutes might be better than 30s.
Serial ports are funny things even ignoring all the wiring issues. 9600 baud is a good speed to start with (at least for 1980s and later) and banging the return key to wake up a serial port isn't unusual although a system console tends to be different.
Please upload the operating system to the Internet so people keep it alive for future generations...
he already did
I will -- but it would be irresponsible of me to do it now as it is filled with PII. We are working on sanitizing first.
Definitely cool if Adrian can upload it but to be realistic, it's Sys V Unix on a motorola 68K, it's not a rare pokemon.
I’m tearing my hair out over here! The error messages are literally saying that the card and disk are not found! The card and disk are on the bench, not installed in the system. Grrrr
I do love Unix and its derivatives!
At this point it is looking for whatever you type on disk or tape. You just have to give it something to boot from, either the kernel or a utility program.
The boot PROM fully understands the UNIX file system, think of it as GRUB in ROM.
You can test whether you need a null modem by measuring which pin is the TX on a piece of equipment. That pin will be driven with whatever positive voltage is used. This works regardless of logic level outputs (1.8-5V) or RS-232 levels (8-15V).
Adrian Is my King off computer ❤
Key works like a car's - turn to to "start", let it crank till it starts turning over, back off to "run"
Those Rifa XT polyester caps shown next to the mains connector on the seond power supply board will be part of a common-mode mains filter. And it is a good idea to replace them with polyproylene caps. Metallized polyester caps are unreliable when used like that.
As I know 9 pin usually for console or dumb terminal and they use XON/XOFF software flow control, printer or hardware 25 pin will have RTS/DTS hardware flow control.
Agreed. The two ports with hardware flow control will probably be for printers and/or modems.
"Lights are not in the rebooting way but in the i should be working way" I absolutely gonna steal that hehehehe, man i like your videos so much!
okay keep watching, just feel the need to broadcast that xD
Hi Adrian, good to see some positive signs of life on that mini computer :) I could see myself falling for the same trap you did with those "loose" Mallory caps 😂 - Enjoyed your reaction to the "blinkenlights", too!
- Hopefully, someone watching can provide or point you at copies of the technical, service and user doco for that model of Plexus ...
- You've already alluded to two places where you expect to have to check and in one case enter values:
- PROM on one the HDD subsystem boards
- Battery-backed RAM on the motherboard
- Will be _very_ interesting to see the results of hooking the MFM emulator up to the interposer, assuming the BIOS will let you get as far as attempting booting from HDD 🍻
Nice to see so much progress! Honestly this could've been split in two, cutting somewhere between reliable serial communication.
Love this journey and your perseverance!
The power supply even has German TÜV certification!
and that from a time when it still was something worth, not like today where you basically can buy that sticker from them...
I may have some tech data on this, we working with these in the 90s they were still running. Cannot say why or where but let me see what I have
I missed Rammy! Glad to see her back!
lame
Amazing that you could resist plugging in the hard drive instantly once you had a successful self test.
Can you put a heatsink on the large resistor that discolored the PCB in the large power supply? Given that the large PSU has active cooling I think it would make a big difference going forward.
There is one thing I've learned watching today. That is... hot snot ...it's a thing that sticks. 😆
Crank it up, Adrian!😂
That looks really cool 😎. Nice vid 👍
For power switches 0 and 1 versus 0 and the letter I. It's binary for on and off. :)