We made some unbelievable discoveries about this Plexus P/20!

[@xxHANNONxx]

Whoever thought some old Plexus nobody ever heard of was going to be peak youtube? This is the best series ever!

[@cathrynm]

Pretty spectacular that Mr. Basement is able to work on this board knowing so little about it.

[@Dukefazon]

It's crazy that there's virtually zero information on these machines, a very few of them exists still today and the one you got happened to have a LOT of vital information kept on an invisible to the naked eye part of the hard drive. Mindblowing discovery!

[@thenerd6192]

I wonder if the hard drive was imaged at the factory, and it was the engineer making the base image who made the typo and put the /user partition at the wrong address, meaning every computer would ship with 90% of the technical documentation in unallocated space. That seems like less of a coincidence than “this one machine happened to have been used by one of the engineers and then got repurposed for general business use”

[@TechTimeTraveller]

That was very lucky indeed! There are tons of small companies that came and went back then and were only known by the customers who used them. The big companies get all the press but often the most interesting stories come from the smaller ones who had to survive on wits and luck.

[@root42]

Similar thing happened to Sierra. Source of the AGI interpreter source on the game discs!

[@danielmantione]

This is a general problem. The 80s were about much more than home computers. A lot of interresting business computers (mainframes!) were made, however, as there was no standard computer architecture yet, there systems had small user bases. Unlike home computers that were carefully stored at attics for decades, the business computers were destroyed after their economic life did end. Companies that made them went out of business. Therefore, we kind of know everything about the home computer side of the 80s, but the business computing part of the 80s is basically one huge black page, with very little hardware and documentation that did survive.

[@Dukefazon]

@@root42 Or they happened to have Al Lowe, who still has the source code for a lot of Leisure Suit Larry games :)

[@johnpetruna8888]

"I'm now in contact with that person!!" 23:15 (This reminds me of when the teenager in "WarGames" tracks down and meets the designer of the WOPR, and together they save...the world!)

[@slightlyevolved]

Adrian meets the designer of the Plexus and together they save the HARIBOS!

[@asanjuas]

One good thing is one video on the channel with this person.

[@xlr8r171]

​@@slightlyevolvedNo Haribo is safe!

[@andycheese9476]

WOPR/Joshua : Shall we play a game?

[@TortureBot]

It's so funny you're talking about War Games because I just saw that on a special that Andrew McCarthy did on the Brat Pack and all the movies they were in during the 80s. Loved that movie along with Cloak & Dagger, Tron, etc.

[@Evergreen64]

For all the fake news and flame wars that the internet has become, THIS kind of thing is what the internet was made for! I love seeing things like this. Because people can be connected to other people with just the right set of skills to help solve a problem! Good on everyone who contributed to this!

[@rommix0]

I love these types of vids. Don't you just love it when a community comes together to get a rare beast working again. From the unix community to the N64 decompilation community, it's incredible.

[@XPbIM3]

-we need a circuitry to pull off a reset signal -lets use the whole 16mhz atmega board to do that! -great idea! Just finished watching: what a roller coaster! Absolutely amazing!

[@horusfalcon]

Hey, when you have a bushel basket full of the things, it only makes sense to use them for everything under the sun.

[@kaitlyn__L]

I thought it was kinda overkill at first too, though I must admit being able to turn a reset loop on and off with the startup key is pretty handy!

[@sparcnut]

Yeah, and that atmega might even be somewhat on par with the 68010s' performance....!

[@paulstubbs7678]

Sounds kind of crazy, like bolting an original PC to the latest and greatest computer just to drive it's reset line!

[@petersage5157]

He did mention that he intends to replace it with an attiny.

[@Dirty_Bits]

The folks in the Usagi discord are a brilliant bunch. So happy to see you collaborating with them. This has been a very exciting and interesting series. Can't wait for the next one!

[@chrisjones8741]

I’m getting “invalid or expired” on the discord link in the description 🙁

[@Dirty_Bits]

Try joining from an Usagi video. He puts a fresh link in every vid.

[@rachelaudrey6241]

Some incredibly smart people, but also some incredibly loud, obnoxious, arrogant ones, as well. :( Can't stand it there.

[@Jody_VE5SAR]

This is a tour-de-force in crowd-sourced troubleshooting. Adrian - this will become a landmark reference in how to leverage modern tech to keep old tech alive!

[@SaltyMeatHook]

Still watching, halfway through. But holy moley!!!! The partition was still there! You are in touch with the person who worked on that machine! The machine was used at PLEXUS!!! Un-freaking believable!

[@argvminusone]

There has been much talk about everything wrong with the Internet these days, but it has certainly succeeded in connecting people.

[@thecorruptedbit5585]

I was reading the wikipedia page about the 68010 the other day, and I saw that someone added the Plexus P20 as a machine that used the CPU, a few days after your first video came out

[@paul_boddie]

Well, now we know that they watch Adrian's videos! Although the 68010 didn't ship in the volumes that the other products in that family did, it was hardly a niche product given the top-tier vendors (AT&T, Sun, Apollo, HP) who used it in their products.

[@xxHANNONxx]

OMG, I hope the person from Plexus comes onto show, and has a chat about it's development!

[@selske23]

I worked on forklifts for a while as an electrician, some of the older machines had so many botched quick "fixes" that opening up the cover and looking at the the wires made you feel depressed, but with schematics in hand I always felt convinced I could find and repair any issue properly. Technical documents are such a big help, especially on complex parts

[@Virnik]

Am I weird just because I find these kind of investigations entertaining, interesting, and actually something to learn from? I grew up in times when these kind of computers were being retired, and new kind of intel-based cpu archs being introduced. I do recall old Motorola CPUs, just not as its primary user, rather than someone who found one on somebody else's attic, and made it work out of shere luck and dumb/blunt will. I am not electrician engineer like Adrian, but I do understand the theory, which makes it easy to 'consume' his content. I do love Adrian's channel. I am computer enthusiast and Unix/Linux Engineer (by job). But these old computers are really something which raises curiosity and interest. Big thanks to Adrian for his streams.

[@Dorelaxen]

Hey Adrian! Met you at VCF this weekend (I was the guy with the "cool shirt")! Thanks for taking the time to chat and get a picture with you!

[@RoyEltham]

What a stroke of luck to find all those technical docs and whatnot for the machine on it's hard drive. Freakin' amazing! :D This series has been fantastic to follow, thanks man!

[@necro_ware]

Wow! Who needs Hollywood if we have such thrillers in Adrian's basement? Very cool! 0_o

[@femboichik]

The Retro computing community working at their best! So awesome, Adrian!

[@donmoore7785]

What you found on the hard drive is truly amazing, as well as the fact you are in contact with the former user of the machine.

[@BaRtJuHh083]

Its so nice to see the internet being used for good things and all the people jumping in to help you instead of being used for scams, commercials bullying extortion and all the other crappy things...it cool to hear all those people joining in to help you figure it out and together being able to probably fix this thing...keep up the great content and hope to see the next p/20 video👍🏻😁

[@TheAnkMan]

I am following your channel since someone pointed me to your "C64 left for dead" video some 5 years ago, and loved every episode since then. Same applies to your series. But this one topped everthing before. How amazing is it to get a machine with virtually zero documentation or any information running again. And the community figuring out things needed to preceed. One has skills in this, the other in another subject. All combined results in awesomeness I've never seen anywhere else.

[@granitepenguin]

This is the kind of series that restores faith in humanity coming together for a common goal. The only thing missing is a Sally Struthers commercial asking for donations.

[@b33zNet]

Lol you said it and I laughed at it... we're old lol

[@Virnik]

@@b33zNet sad fact. as long as you can make a new step, you're good. Being 'old' is just a title. What you'll do with it matters. The title itself doesn't.

[@horusfalcon]

@@b33zNet "You wanna make more clock cycles.... sure, we all do!" 😁

[@argvminusone]

This sort of thing gives me hope. If we somehow do create a Star Trek post-scarcity society where no one has to work, people won't all just sit and watch TV all day. They'll find something interesting to do. The drive to discover and accomplish will still be there.

[@Colin_Ames]

What incredible luck finding those documents. Also, what incredible luck having community members willing and able to search for them. I am waiting with bated breath for part 5.

[@Hutschnur]

I just can't get enough of this stuff. The machine is a stunning beauty inside and outside. Thank you, Adrian, for sharing!

[@Cherijo78]

IF ONLY SOMEONE HAD A PDP 11 TO RUN THE CALAY CAD ON... Usagi.... Looks like your mission is clear...

[@anotheruser9876]

So ERROR 4F02 was the location of the chip on the PCB (Row 4, Column F).

[@KameraShy]

Very logical.

[@kaitlyn__L]

Ooh, great spot!

[@perorin615]

there is absolutely no way that's what the error code means

[@kaitlyn__L]

@@perorin615 I mean, we’d need to see if the causes of those other, non critical, errors also matches the maybe-pattern.

[@perorin615]

@@kaitlyn__L the system doesn't have access to individual chips. consider that the bad signal went to the working PAL chip which outputs a good signal. How's the system going to know that the signal between the latch and the PAL is bad?

[@MartinsGraveyard]

Adrian, I'm so happy that you've decided to do this full time, some time ago. You are perfect the way you are, and watching you is a pleasure, even if I don't get a lot of it. Bounding you to some office job would be a huge waste for humanity. Thanks for the great content!

[@wysoft]

I think this is one of the funnest series you've done so far - even if you probably never intended to have to pull so many strings to get this thing to work - but I love these old oddball Unix systems any way. At this point you're almost into the territory of one of those "we found this 100 year old truck in the woods will it start" videos

[@jeffvandyke8162]

This has been one of my favorite ADB series in the last several years!

[@godfirnon]

This series and your entire description of the troubleshooting in the middle of the video are absolutely riviting!

[@AntonyTCurtis]

More accurate to say that the 80286 only supported segment based protected and virtual memory where entire segments can be marked as not-present while the 80386 added page based virtual memory. If the clock chip isnt ticking, the OS will not be able to measure how many loops in a second... it will wait forever for the time to change. Check the 32.768KHz crystal.

[@rdog77]

The saga on this series is got me hooked! I do a lot of troubleshooting in my younger years, all gone away. This brings me back. Love this channel.

[@vwltfluxcapacitor]

Adrian - this is unbelievably fascinating. Thank you so much for sharing!

[@maxtornogood]

It's fitting you have Rammy off in the corner given the nature of this issue. Lots of excellent sleuthing & forensics finally led to a breakthrough. The saga continues!

[@KameraShy]

Truly amazing engineering back in the 80's. Reverse engineering this mystery machine is uber geekdom at its finest. There are no limits as to what can be accomplished.

[@bikeforever2016]

What a fantastic set of results. Saw you pop up on Usagi's discord and tried to keep up with the unfolding of events, but it was fast. Loving the series. Encouraging me on my vintage computer journey. All the best.

[@rager1969]

Wow, you lucked out on that hidden partition. It's like finding the Rosetta Stone.

[@calinculianu]

Adrian -- this is one of the best video series you ever made. I LOVE IT! I love the mystery and the success story of the community coming together and the plot-twist of the technical docs being ON THE MACHINE ITSELF. This is a great series!! I don't even want it to ever end and I look forward to the next part.

[@johnvanwinkle4351]

Great troubleshooting! I appreciate you actually trying to figure out what is wrong instead of changing parts and seeing if it fixes it....grin

[@JohnnyUtah488]

I always enjoy Adrian's videos, but this series is absolutely EPIC! It's so wholesome to see the community come together to unearth this piece of computing history. Kudos to everyone involved!

[@3vi1J]

That's some amazing crowd-sourcing and detective work. I can't wait to see the next steps. And, it was great meeting you today at VCFSW; hope you come back for more panels/talks at the next one!

[@nemike42]

Is it coincidence that the error 4F02 is the same as the socket that the chip was? U4F ? Did the error actually indicate the failure location?

[@CollinBaillie]

When I looked in on the Discord, the working theory was that the numbers related to the test sequence. Test phase 4 was named Main. F was Failed and 02 was test 2 within phase 4. So the second (or 3rd, starting at 0?) test had failed.

[@NEEC1]

It looks like it, but how sophisticated would the diagnostic routine have to be to be able to drill down that far. How about pulling another chip, see if the diag code gets it right. Easy test.

[@AnthonyRBlacker]

I MISSED this drop, I've been waiting for the next Plexus video, it's crazy there's like zero info on these things out there, but it's SUCH an exciting machine!! I hope you get it working.. so cool

[@VincentGroenewold]

Absolutely mindblowing again. I never cared for PC-like machines back in the day, but this machine is super interesting, so much thought went into it. Love it!

[@pmNCC-1701]

An easier and simpler way to remove a chip for replacement is this: Take a very sharp and new side cutter. I keep this cutter just for cutting I.C. pins. Cut all the pins flush to the body of the I.C. The body falls away. Then take a needle nose pliers and a solder gun, heat a pin at a time, and remove each pin from the board. Next, take a solder sucker and remove the solder from each pinhole. Be careful not to overheat the pinhole otherwise, the trace and or donuts from the board will lift off and break... I have been using this technique for decades... =)

[@mikebarushok5361]

I'm still always amazed when I see people that don't use that method struggle and often damaging traces and plated through holes.

[@KaldekBoch]

Is that T-shirt from "The Grouch" for Mac? Damn that is OLD school.

[@ericshapiro340]

Hey, who are you calling old? :-)

[@brooknet]

I'm so glad that you made progress with the RAM issue! May I add that I learn a lot from the way that you troubleshoot these complex systems, and it's valuable information to help when I am trying to diagnose issues with my computers. For example, I may need to troubleshoot a SPARCserver (630MP) that I haven't powered-up for three years. It has a real-time clock module that's similar to the one on the Plexus: it's a sealed unit, no way to replace the battery when it runs out. There might be some hints on how to access the battery terminals. All this fun stuff awaits. The trouble with the 630MP started when it was invaded by tiny spiders. 🙂

[@insanelydigitalvids]

A gift from the Universe + a team of geeks + a Master Class in tracing circuits = excellent video! 🙂

[@packetman]

This kind of stuff restores my faith in humanity. When the computers take over the world, they will remember these people in a good way.

[@mistermac56]

Great video Adrian! Hats off to the many contributors that are providing great information. It put a smile on my face when the pop up message came up and said that you are in contact with the designer. I sincerely hope that they can give you insight into the Plexus. It would be a gold mine if they still have schematics and/or design information to help you totally resurrect the Plexus.

[@WouterR]

Wow Adrian, i’m technical and love your videos. This video is really next level, you lost me quite frequently. But the fun you have recovering these old gems is remarkable. Greetings from the Netherlands

[@KameraShy]

This really is a hard core computer design 101 course.

[@AnthonyRBlacker]

13:15 it can be a daunting task. BUT.. as long as you've done your due diligence and wrote everything down, now YOU are the one who's written out the schematics of all the ICs on that board. What great work Adrian.. it takes a special person to go through all that..

[@MarkyShaw]

This now the Plexus saga! :-) I'm fully invested now.

[@delmonti]

....this is better than ANY Netflix series!

[@Kwaq84]

Oh come on, Wednesday was pretty good and wasn't fu@&ed yet ;)

[@dcfly]

Adrian, I love your videos. Unfortunately, I live in a small apartment in the city. Believe me, I have exhausted my space with old computers. Your channel allows me to live vicariously through you and your troubleshooting. I am fascinated with the computers you get to work with, even though I have no room for them myself. Your troubleshooting methods are exactly what I would do (or better in most cases). Thank you so much for your videos.

[@tristanbuckner]

This series has been so exciting I ended up ordering Lions’ Commentary on UNIX.

[@exidy-yt]

It seems like that whole 'battery damaged' area suffered a failure. I think you have a couple more S and LS logic chips to replace! So happy you have Usagi's discord helping you out. Those guys are fantastic and helped Dave bring a Centurion mini almost as obscure as your Plexus back to full life and emulated and documented. I know you will get this finished, especially with your incredibly lucky find on the HDD!

[@SidebandSamurai]

This is majorly cool. Adrian, you are awesome. You could write a book on this subject now, because you are the SME (Subject Matter Expert) all the people who own plexus's will come to you for your information. Good luck in making this old machine work.

[@morebasheder]

I just love the endless enthusiasm that you have for what the vast majority of people would consider to be obsolete junk. Clearly myself and other viewers of this channel are in the same category as yourself. Keep up the good work! Greetings from the UK 🇬🇧 👍🏼

[@gregorymccoy6797]

This is exactly the type of discussion I love. Thanks!!!

[@baronvonschnellenstein2811]

Solid progress! Glad to hear you had some good luck w.r.t. a form of original documentation hidden on the HDD as well as getting a line of communication with someone formerly involved in the design/build of the machines - as well as some helping hands in the wider retro-computing community :) Eagerly awaiting the next instalment of this adventure!

[@johndoe4314]

This series is so great. I was hooked by this machine right from the start and how this story unravels is just superb. I love how you get the community involved and that we bring this thing back alive together. And if anyone could have its own emulated P/20 would be soooo cool! What a great series Adrian! Thank you all!

[@timothyp8947]

I love this computer archaeology trip! Having spent time at college and my first job with Sun3 Workstations and even the odd MicroVax, this kind of small Unix server fascinates me. How amazing to discover all that technical material still lurking on the disc!

[@woodybode3621]

The CAL.CE- signal is not about power savings. Consider the case when the system is being powered up or down, and the voltage is out of spec for the ICs (less that 4.75 V if I remember correctly, tho they typically could run on a little less) There is no quarantine the Clock memory would not be given a bogus write command, destroying the configuration. The CE is active low, which makes it a bit of a pain, as we want CE- to be high whenever the power is out of spec. MRESET- from the power supply is the "gold standard" "you got good power" signal, which laughably is broken in your box. The transistor/pullup resistor is simply an inverter to lock out the clock memory. You did a superb job!!

[@Skracken]

You and the guys helping you figure this out are just brilliant! True hackers! I'm neither smart enough nor patient enough to do what you guys are doing, so I am in awe! Looking forward to see if you can get it fully functional again. Thank you for keeping these relics going.

[@McTroyd]

This is phenomenal Adrian. Finish line in sight! Keep it going. 👍

[@teekay_1]

Outstanding work. A lot of these "mini-computers" from the 80's are lost and forgotten, and since they were before the the internet, there was nothing to save by the time these companies went bankrupt. You're saving a little piece of our computer heritage with these videos. Thanks much.

[@BrianOrange]

Holy crap Adrian, this might be the best video you have ever made. I learned a lot today.

[@Groovewonder2]

You said you were in contact with the original user of the machine, so it would be REALLY cool to get them on a video call for an interview. Get the real backroom information on the history of the machine and its development/production.

[@UCm0i6w5lBlRthCtZEoj99tg]

Really loved this series! I'm so glad so many people came together (especially old Plexus folks) to get some of this figured out.

[@michaelhaardt5988]

What an overwhelming series of events! That may be the best episode series ever and you had quite a few brilliant ones before.

[@lathans1]

I can't remember the last time I was so interested in a series of anything! Or had me that excited and wanting more at not only one, but every cliffhanger! Thank you for all the great content!

[@kilgoar]

this is now adrian's digital archaeology. love the professionalism in the approach, the keeping of records, and publishing of results. there are some things worth more than a working machine, and this machine is like cracking open a rock and finding a transitional fossil

[@GeorgeWMays]

Progress. Congratulations. Keep chugging. I'm impressed. Thanks a ton for the video. It's appreciated.

[@AntneeUK]

I honestly did not realise that I'd watch multiple hours worth of videos about an obscure multi-user Unix machine from the early 80s, but here we are

[@Brian-L]

How fortuitous to have found the technical documentation on the very (broken) machine for which no technical documentation exists. Computer inception immediately came to my mind too. 😂 Great work tracking down the flip that no longer flopped.

[@parrottm76262]

Keep on keeping on, Plexus P/20!

[@Eremon1]

It only just occurred to me now, but with all those bodge wires, is it possible this is an early model? Perhaps it never made much of an impact in the market not selling many. Thus the reason there is literally no information online about this particular machine. What an amazing find on that original partition. The fact it survived all these years is just mind boggling. I don't know why, but when an old forgotten machine gets some attention again I find a lot of satisfaction in that. Cheers.

[@brandonbrooks2845]

It was a pleasure meeting you at VCFSW on Saturday!! Great job with the Plexus, what a treasure trove of information!!

[@MrAsBBB]

Don’t you just love Aidan’s diagnostic expertise? I have to diagnose problems with software systems everyday and it’s what makes work fun as so far, nothing has eluded me so long as it’s in my sphere to solve and fix. The enjoyment is infectious. Best Regards Alex.

[@jeromethiel4323]

What's amazing to me is a single transistor on a chip can break an entire machine. Considering that modern computers contain millions of transistors, it's amazing any computer works at all. But they do, and continue to work for years and years. Semiconductors are amazingly resilient as long as you treat them right.

[@jeromethiel4323]

@yt45204 Now, yes. But when the Plexus was built? Heck, modern memory has billions of transistors in them alone.

[@johnfox4376]

You were the one who said that "modern computers contain millions of transistors".

[@jeromethiel4323]

@@johnfox4376 Captain pedantic to the rescue! Yay! You win the internets.

[@IMJustSomeGuy100]

Amazing that someone’s mistake turned into your lucky break! I could never take on something this complex but it sure is interesting following along.

[@perhansson6718]

What an amazing journey Adrian! Thanks for making such a detailed recap of the troubleshooting, looking forward to what can be crowd-sourced on the Discord server :)

[@greenmoose_]

I have no idea why I am so invested in the story of this machine but I clicked on this one fast when I saw it! cant wait for the next instalment!

[@andrewrfpi]

My goodnes, you are the man! what fab diagnosis! good luck with the next steps debugging the multibus / clock issues.

[@lindoran]

Just Bonkers! Wow! Insidentally that negative set reset JK flip flop is a common part in a lot of reference Motorola designs. The E series 6809 uses a similar style flip flop for building the clock generator for E, Q and with the addition of a 7474 and a 3 input nand handling of the MREADY line. I got to say a huge thanks to everyone who pulled together to make it this far! Well done team 😊

[@doughobbs7706]

jeez you are going to need a holiday after this thing is sorted - just amazing!

[@DanielLopez-up6os]

It's awesome that people were so willing to help to make this one work.

[@ukaszrutkowski8368]

This computer deserves its own name. An it should be "Hitchcock" for sure.

[@Choralone422]

Incredible work done by everyone in the Discord server! I am so pumped to the new developments in this video and those yet to come! It has been so satisfying to watch everything come together to help understand and document more about this machine! So cool!

[@djwaffle]

I appreciate that you are being careful with data on the drive. Great work.

[@moemlm]

enjoyed every minute of the plexus series, cant wait until we can process some documents on Q-office

[@pelgervampireduck]

wow. I'm from the "x86 PC" universe, this is alien to me, I think I'm not understanding half of everything, but it's so fun and fascinating!!!. it's like you are reverse engineering an alien spaceship. this series is awesome, and I love how the community is helping and all the effort, and the good luck!. the hard drive working was like winning the lottery. it's great your work helps historical preservation too.

[@GYTCommnts]

This is INCREDIBLE and one excellent example of community knowledge and team work. Amazing! ✊

[@dr.klipper]

I love this Plexus series :-) Can´t wait for part 5 now ... Well done Adrian 👍

[@AxelWerner]

What are the odds!!! amazing collective work everyone!!! You guys are WIZARDS!!

[@lithiumpro9999]

great job.. This is why i love your channels.. Watching you retrace it and even if you fail this is great stuff.. Because we only learn from our failures..

[@binaryguru]

The 555 is still made and is very easy to use and requires no programming. Great little IC!

[@jedglover8245]

I worked on UNIX systems like this in 86, amazing job to get it to hopefully the verge of working again. Interesting that 39 years later 4kb is still the default page size for Linux.

[@CH4NNELZERO]

Cool. Were you working on the hardware design or the software back then?

[@jedglover8245]

@@CH4NNELZERO The company I worked for did software for insurance brokers, the system we had was a Zialog Z8000 based UNIX, very similar besides that. I think it was tested as a possible new platform for customers, but we ended up using Thoroughbred Basic on IBM ATs. The systems being replaced were Mercator systems running Mercator Business Basic, that was identical to Thoroughbred Basic, all ISAM table storage.

[@No-mq5lw]

Think that's mostly because x64 still only supports 4k paging. M1 supports 16k.

[@jandjrandr]

So amazing. It is a pleasure to see the community come together and breath life back into this system. It will be fun to see and hear more about this beautiful piece of Unix history.

[@grinderkenny]

I just love all the old unix stuff.. very cool series