Dave buys a PDP-11/34 from eBay and adventure ensues! For my book on the spectrum, see: amzn.to/3XLJ8kY Follow me for updates! Twitter: @davepl1968davepl1968 Facebook: davepl
How about when an engine hoist is far to small to lift it or move it? I once had a VAX 11/750, brought it up to the third floor to my apartment, only to misassemble it by connecting the PSU main fan airflow sensor to the wrong port blowing the thing. By brought up I mean I disassembled the whole thing and brought it up piece by piece using the stairs, I had no elevator. But about the same time I also got a PDP 11/23 which worked a treat. The VAX ended up at the dump because of the airflow sensor, there would have been a way to cheat it and get the main stage of the PSU to power on, but it was far beyond the means of a 16-17yo me. I lived alone at the time and had about $40 a month to live on, which was enough for fast cook macaroni and ketchup, and some ramen in the weekend if I had been frugal. Still feel bad about the VAX going to the dump, but that's where it was headed before I tried to save it and failed.
@@naikrovek what do you mean by 'mainframes'? Also, most systems are not really vendor locked, so not sure what you mean there. Some software is hard or impossible to get as a private person but most of that doesn't stop you from running them, just stops what you can use them for. Like some compilers are nogo, some specific functions on for example large IBM systems like LPAR require feature unlocks by the vendor, meaning if it's not unlocked when you get it, you won't be using it, and if it is unlocked it won't be if you upgrade or reinstall the OS in certain ways. Most of those things you can work around if you know what you're doing, without help from the support. Or - ehm - official support at any rate, it helps if you are not totally some unknown guy 'off the street' to them.
PLEASE more DEC ANYTHING. I was with DEC for years from PDP 8 series through most of the VAX series. I know these systems frail to most simple systems now in some ways but the evolution of DEC over the years was amazing. I am happy and honored to have been part of the excitement. In case you may be interested Ken Olsen did everything to keep the payroll running even when times were tough and we did have some lean times. He made some errors in judgement by not getting in the PC biz earlier but there were no crystal balls then and as they say, it is what is or was, as the case may be. Thanks for keeping some of the DEC gear going and preserving the tech on your super neat YouyTube channel !!!
I feel that DEC trying to get into the PC game was one of their poorer moves. This is not the venue that DEC was great at. Too many companies tried and most failed at the PC market. I worked at Sperry and they made one. Never really went anywhere but it seems they thought they had to try. I wanted to work at DEC but they never contacted me for an interview till I was already at Sperry for several months. I am a big DEC fan. I learned computers on the pdp-8i running TSS/8. Later got into the pdp-11 line and then then pdp-10 (KA-10). I have the pidp versions of each that Oscar sells. They are miniatures of each but with the same but smaller front panels and switches. I have one big pdp-11 left.
I wanted to work for DEC after seeing a VAX 11/780 at the lab my father ran, but ending up taking a different engineering subject. But did end up using microVAX IIs and Alphas during the 1990s. I'm wasn't a systems engineer but was able to do some pretty cool things with the cluster, the ease at that it was possible to log onto one computer and then run an application on another computer, using the hard disk from another I still find amazing. We did have DEC PCs, but I doubt they would have saved DEC. I've heard that Ken Olsen was a decent guy, again marking out DEC from Bill Gates and Microsoft who haven't innovated a single thing and every product is stolen or cheated from somebody else.
Still under warranty, right? Wouldn't want it breaking and struggling to get parts... I wonder if the warranty registration card would work? Just imagine someone's face getting that...
It's scary to remember so many operational facts about these computers. In the early 80's I got hired by a 3rd party DEC service provider as a bench technician fixing VT-100 terminals. After fixing all the broken terminals on hand. I turned to work on our 11/40 test bench machine which had been down for nearly a year prior to my arrival. I taught myself how to repair and operate the machine and in 9 months became the company's senior field technician. As long as I had test equipment, schematics and coffee I fixed most everything I was thrown at. Floppy Drives, Hard Drives, Tape Drives, serial controllers, line printers, power supplies. These machines had modular switching power supplies that would fail pretty frequently. I built electronic dummy loads that dissipated power through 2N3055's strapped to massive heatsinks with fans blowing on them. It was a great time working with these work horses. Thanks for the memories. I'll watch any PDP-11 video you put up. Cheers.
Hi Dave, I'm a PDP-11 fan, specifically the PDP-11/40 running RSTS. Please make some more videos showing your adventures with the PDP-11/34. If memory serves me correctly, when you pull out any of the rack drawers with the cards in them you can pull the "T" handles on both sides forward and that will allow you to rotate the draw with its backplane and all of its cards 90 degrees so you can easily access the bottom to see all of the wire wrapping. If you need to put that wire back on the backplane there are wire wrap tools and wire radially available on eBay and other places.
I started at DEC in the Netherlands in 1980. RSTS was the first OS I worked with. I remember that you had to prefix commands with "please" on the console in some cases. The console was a LA100. Patience was a good quality to have in these days.
.. would the emotionally neutral narration have something to do with being on the spectrum? I for one enjoy it as well, it's well suited to run a channel like this ( or a teacher.. though there it's hit and miss if your students appreciate the bare bone business approach or if they want their fragile egos touched lightly and with 'consideration' ). ps I'm on the spectrum so are both my kids so nothing negative meant ;)
I was a coop student in the late seventies, working for the DEC manufacturing facilities in Puerto Rico. Our factory used to create PCBs from scratch, many for all the series of DEC PDP computers ever made. On my first day at the job, they gave me a Simpson meter and had me look for shorts and opens on many of the boards they manufactured. I worked with some of the smartest engineers at the time. If you look and find circular stamps with the letters SG or AG, the board was made in Puerto Rico. At one time, they began work on PCBs for the VAX line of computers. One computer that never saw the light of the day was the PDP 11/77. It was a dual-processor version of the PDP 11/70. However, it was canceled because it was too fast compared to the PDP 11/70. This was one of the best jobs in my EE career. 173000G!
Fun! I really appreciated that photo of the PDP-1. I read where the guys at MIT, when they got their new PDP realized it had a "scope," so they wanted to create a program to demo the capabilities of that scope. They created the very first video game, Space War, using model train controllers as game controllers. I've previously seen only black and white photos of that model. I first learned Microsoft BASIC on an Ohio Scientific minicomputer that our tech school had in a back room. For seven years I was the operator for a series of IBM System/34 and System/38 minicomputers. For five years after that I was the lead operator of an IBM AS/400 Model 70 supermini shop. We were trying to demonstrate we didn't need no steenkin' mainframes. But we were pushing those machines hard. The guy from IBM said we were considered to be "hot-rodders." I would love to see you boot up UNIX on your "new" machine. They invented C to enable them to port UNIX to different computer architectures.
Funny you say this. Just before DEC Magazine became the VAX Magazine, they accepted an article from me, on reducing boot speed to < 30 seconds for the PDP-11/34a. My trick was to change the defaults in the O/S source code for the terminals to be our settings for 28 of the 31 terminals we had. So we got rid of ALL of the TERM SET BAUD 300 ... Lines. Then I rewrote the numerous one line commands for the UTILTY short cuts, etc. etc. To be a small assembly language program that read in one file for each set of settings. And processed them without loading/unloading the same program 20 times in a row. I also pointed out that if you could not change the "SIL" (compiled OS). Then you would benefit from changing the terminal command to operate on a RANGE of terminals (2-28) and allow multiple settings with a "delimiter". Again, running a program once, and setting 28 terminals in a loop. Versus launching a program for each setting for each terminal. Although the article never saw the light of day. It was very educational as a High School Student to learn to write, re-write the article. And to thoroughly test the code. Add timing to things, and figure out that the Assembly Language helped, but the biggest thing was simply loading one program to do all the work with one invocation. Once I learned that... I was PUT OFF by how the original startup file was setup to do the exact opposite. I knew from those days 40 years ago. I would do this stuff for life! And I still love it!
@@yoursredIBM was a huge monopoly and there was a saying "Only IBM made Computers" Hence, Dec marketed it as PDP and Wang Labs made "Calculators" to protect themselves from being bought up by IBM
I know of a department that bought a model PDP8 Oscilloscope as they were not supposed to using computers. Order was signed by the boss who never caught on. The salesman was happy to play along.
The story I heard is the venture capitalists in 1957 thought a “computer” was the huge room filling million dollar systems dominated by a few companies like IBM, UNIVAC, etc. Nobody wanted to invest in an unknown small startup company with only a dozen employees to compete with those huge established companies. So DEC didn’t build computers. Instead they made Digital Laboratory Modules / System Modules that could be plugged into a backplane in a cabinet and connected together in different ways to make specialized laboratory equipment. The fact they just happened to also sell the “Programmed Data Processor” (PDP) cards that would help coordinate their Analog to Digital, serial, disk drives, and other cards was just a “coincidence” … at least to the investors.
I only have seen the PDP-11 as a number cruncher for Mass Spectrometers. In the 1990s I was a field engineer for Hewlett-Packard and VG Mass Spectrometers, so there were plenty of these machines collecting data and crunching numbers to present the graphic output. It is always good to see a "Lazarus" booting. Lazarus have come back from the dead. One observation. I would very much take care of static discharge when working on the boards. It is worth buying a carpet for you to lay down the boards and use the grounding straps. I am very happy it worked for you.
Yes, my dad had a PDP11/34 in his lab connected to a mass spectrometer. What you described was its exact roll. He told me it was very pricey and the annual maintenance contract was also costly. Fortunately in Canada the Federal Government was paying so it was treated very well. I believe Dave indicated during his board pull that one was a A/D board, so that’s likely the board interfaced to the mass spectrometer. Hopefully he can pull up some m/z (mass to charge) spectrograms. Looking forward if Dave can dig up something off his machine especially if related to mass spectrometry.
Back in the 70s-80s I was a field engineer for Burroughs. They sold a high volume laser printer OEM'ed from Xerox. It used an 11/34 as a controller. There was a 9-track tape drive for reading print files from the mainframe and a disk pack for software.
I first used a PDP-11 in college at 17 ish, that would have been 1984. I wrote a Z80 emulator on it for my final year project (I was a confirmed Sinclair fanatic). There was a much larger PDP-11 (70 I think) at Polytechnic, and then I moved on to VAX’es when I started work in 1989. They were superb machines, and I fondly remember them. Manuals! Real, proper manuals that told you everything. Being a true geek I learned VAX Macro assembler and wrote a modem driver in it - this was used to communicate between remote sites in the UK. I think my finest hour was patching an RMS database that was corrupt for a water company in Eastbourne. All in all, I loved it. And I retire today! Now it’s pet projects that will keep me busy, I can’t wait! Thanks for the content Dave, you never cease to be inspiring and interesting.
I remember the Sinclair. I used one as a prime number generator. I wanted to find the largest prime number the Sinclair could produce before the program bombed. At first, I was getting a new prime number every few seconds, to where it would take days to calculate the next number, fun days of my youth.
When I was in college the PDP-11/45 that we got out of the trash at Bell Labs (I realize this is a lot to unpack, also we totally didn't Redbox the call to Bell Labs to arrange for the pickup) we disassembled everything and moved it all piece by piece. This was much easier, it also helped to have a house full of college students. I am really happy that you got a big PDP. It brings back memories for me. We ran RT-11 on ours.
The first computer I ever got to play on was in 1977 and was an 11/34. I was located in an office in Adelaide South Australia and the 11/34 was in Sydney New South Wales Australia, over 720 miles away. My access to the 11/34 was via a Decwriter LA36 printer/keyboard. The cost of interstate data links in 1977 was enormous, so my link had to be only 300bps and was only available between 12 midday and 1pm and again between 4pm and 5pm weekdays. The government monopoly telecom service would use a manual switchboard operator to plug in the link at the required times each day. Needless to say this often didn't occur, so I would complain and after a while they simply left the link up permanently. As a result I got a full time connection between Adelaide and Sydney for 1/20th of the normal cost for several years, so I was able to play on the 11/34 all night and all weekend, which I often did. Thank you so much for this video and yes I would just love to see anything more on the 11/34 you would like to make.
WOOHOO! (Sorry, I couldn't stop myself! I just got to 26:45 and the DIR listing appearing! I'm so absorbed in your storytelling Dave that I feel I'm actually there with you! 😂)
me too, I updated a BIOS the other day, from the 2014 version to the last one, 2018, (to get UEFI working) and it booted right up and I was PLEASED (-:
One of the first computers I ever worked on. I performed maintenance on these, their punch tape readers, tape drives, monitors... ect. Regarding your disk drive, their heads would drift out of position on a regular basis. If not realigned every six months or so you'd find that disks archived a year or so back could no longer be read. The same would happen to the reel to reel tape drives, a real pain when trying to recover a crashed disk. Thanks for the video and memories.
Congrats on a fantastic adventure Dave! When I was in Grade 12 in Ontario in 1983 we go one donated to our high school. We were in heaven! Keep on your great PDP journey! "And when in doubt, reinitialize the MUX!" (Oops. That was for an HP Mini at Environment Canada )🇨🇦
I'm a huge PDP-11 fan. I'm living out my fantasies through you. Thank you. The PDP-11 machine code language was my favorite. This all stated in 6th grade when I wrangled a subscription to the Digital chip manuals. I was once able to program through the light panel, but alas those skills are hiding somewhere deep in the recesses of my brain.
I started my IT career by using a PDP 11/70 running RSTS/E in high school. I loved that machine, just about everything ran on DEC Basic. I still remember using PIP commands to set files attributes to move my programs into the 1,2 account so they would run privileged. I miss those days.
Sometime I need to port the old Star Trek for VT52 to something a bit more modern. BasicPlus and the explicit VT52 escape codes are a bit annoying to figure out having not used that part of my brain for over forty years.
@garry4086 ditto ! A similar road travelled for me via a high school with only 1 Teleray terminal + dialup 300bps modem to an 11/70. Yes I remember using peripheral interchange program (PIP) too. There was a large library account of game and education programs in "basic plus" had star trek for vt100 no need for escape codes of course. It was just the thing to motivate a teen to start teaching yourself Basic ;-)
I agree. I was hit with a wave of nostalgia at the mention of wire wrapping. During my college projects in the mid 80s I was wrapping (and unwrapping) probably a zillion little blue wires, and found that the curly pigtails of unwrapped wire wrap wire when tangled with carpet fibers are almost impossible to extract from the carpet. Good times!
Absolutely! Shout! Thank you for the content that you create! I journeyed the PDP 11 line (as far as my budget allowed) about 10 years ago with the /03, then upgraded the backplane to a 22bit bus and continued with /73 and /83, ended with blowing up my coveted scsi card and parked the rig in the corner of my shop. Adventuring a PDP 8/m currently. Thanks again!
The PDP11 was the first computer I ever had access to in High School, found I had a love and knack for programming.. Some 50 years later I'm still at it. Thanks for a great video.
My previous employer, at one point, had multiple PDP-11 stacks in our server room. By the time I was brought on board in 2006, the environment was emulated, but the machines were still there. I had a chance to look them over multiple times before they were eventually fully de-comm'd. I learned a lot about the environment because of the emulated stack (a few of our manufacturing systems required a PDP-11 "backend"). I've heard hundreds of stories about these things, from people programming them, to troubleshooting the smallest of software glitches. (Who dropped the cards??!!) Eventually, in 2020 (during COVID) we removed the legacy system at the one remaining plant that needed the emulated environment to operate. I gained a ton of respect for these machines in the process. That "system" (even if emulated) carried us through all the way to 2020.
Thank you Dave, I was hooked at the title. My 1st job (as operator) was to run software builds of realtime SCADA systens on various models of PDP11s. Your adventure brought memorys of talking with DEC Technicians who were adjusting or repairing the devices on machine room floor. You triggered memorys from the 70s. I follow what you post & PDP11s are a sweet spot. Thanks.
That's great. I had the job of building a network of SCADA systems across many corporate sites in the UK that communicated with a PDP11 using packet switching. The network was later sold to one of the UK telecoms companies and was still operational nearly twenty years later. I can't imagine the SCADA and PDP11 lasted that long though.
In late 1970’s I (plus two other programmers) was using a PDP-11 to cross-compile Z80 assembler code for computing integrators that our company manufactured. Machine code was on paper tapes punched on the PDP-11 and then read at the development station to test and debug the prototype system. At one point I wrote a BASIC interpreter so the program that generated reports could be written in high level language. A computing integrator was used in a chemistry lab; it takes an analog signal from a chromatograph and produces a report showing how much of each expected chemical was found in the sample being analyzed.
Thumbs up so hard!! I've been watching Usagi Electric slowly get his PDP working and its been enthralling. This thing looks amazing and I can't wait to see you dig into it. I'm voting right now for getting some ancient Unix running on it
Holy smokes, before this episode, the only other time I seen an engine hoist used on a rack was at the STP Nuclear generation plant here in Texas, on an old fully stacked Sun rack. Bravo gents!
One of my favorite computer memories is playing Adventure on a PDP 11/34 at RCAF HQ in Ottawa, Ontario circa 1977. I think I have a spare wire wrap tool somewhere if you get desperate. 😊 Ideas for what to do. Go on a tour of Colossal Cave.
OMG I cut my teeth on this machine! Not that I knew much about computers in those days. We took one to sea in 1977 on an NSF funded research boat, and sailed with it for several years thereafter. Thanks for the memories.
I"m a longtime UNIX nerd and have fond memories of the DEC Alpha cluster that my university acquired in the early 90's. 384 MB memory, who could imagine such riches? So I'd love to see UNIX on this old box if that could reasonably be done. Thanks Dave, love your channel.
This takes me back 40 - 50 years when I had tech jobs maintaining and repairing everything from PDP 98s and PDP 11's . Watching this video showed just how much I've forgotten over the years. Gone are the days of the Honeywell 516's, General Automation SPC-8 and 12's, and the Varian 620's. Thank you for keeping these systems alive.
As a retired tektronix engineer who started in the PDP-11 era, I’d say if you can find an old working tektronix direct view storage terminal (dvst) and the software you could load the old lunar lander program that simulated landing on the moon from orbit and displayed the lander on the terminal. Used keys to control engine thrust. Don’t know if it would work with a current generation terminal program that has a tektronix graphics emulation mode or not. I wasted hours with this. Surprisingly hard to land in one piece! There was also a text only adventure game. Can’t remember the name, but you could explore and pick up treasures to use in future battles. I remember I keep getting stuck in the maze of “twisty turny little passages, all alike” - assuming I could get through the maze of “twisty turny little passages, all different”! Spent hours on that one, and I don’t even like computer games! Of more modern games, the only ones I ever play are solitaire and occasionally Tetris!
That game was “Clossal Cave” by Willie Crowther. I had a version written in Fortran (including Source!). I was the one (by a real stroke of luck) to finish first. Charle Drum - are you out there? It was a GRAND time and CC and the PDP-11 live as beautiful memories of mt early years becoming a programmer. 😊
I almost bought one at the DeAnza College, Cupertino CA swap meet in 1980 $800 with 2 disk drives (removable). Wanted to run a multi line BBS. Never got to run one at work, We have Vaxes, lovely machines
3:50: $120,000 in 1960 is equivalent to about $1,250,000 today. $0x131AB8, to be exact. Yes, I know they used octal back then. I used to work on a 11/73 with a colour text display-was it VT320? VT520? I don't remember. RSX11M+. SYSGEN. MCR, EDT and MACRO-11. QIO$S. The TKB linker. SY:[1,54]. I'm surprised that I in fact remember this stuff...
The VT320 was a flat screen style monitor that came in 3 flavours of display; amber/black, green/black or paper white, which was fab, the VT340 was the bigger, colour monitor.
This video brings back memories. I used to work for a computer company called Evans and Sutherland (short name for the company was E&S). I was a field service engineer for them in the 1980’s. They had a computer graphics system called PS2 (Picture System). The PS2 system had an unibus card for interfacing to the PDP 11 series systems . This card used the what I thought of as the interrupt signal, what you are calling the NPG I believe. Yes it was a signal wire that was wire-wrapped on the older unibus slots, and daisy chained to each slot. I had to also cut this wire during first install of the PS2 systems. To re-wire-wrap the pins you would just need a wire-wrap tool along with the 28 or 30 gage wire. I used to maintain these PS2 systems with the Unibus cards in DEC PDP 11/xx models as well as DEC VAX systems with Unibus adapters for backwards compatibility with the older PDP 11 systems. Thanks for the video as it brought back lots of good and bad memories 😁. I would be interested in more of these types of videos.
Love these DEC episodes. The first computer I was exposed to was a PDP-8 in grade 9 where we learned to do simple programming with paper tape. At college we had a minicomputer class where we did software and hardware on an 11/70 and 11/34. In third year we build add-on memory for the 11/70. My first job was doing airborne geophysics and the system in the aircraft incorporated a ruggedized PDP-8 clone. A subsequent job involved programming and supporting a LSI-11 based on-stream x-ray fluorescence systems for mineral processing plants around the world! Many years of hardware and software fun (RT-11, RSX-11, Assembler and Fortran). These DEC shows bring back a tidal wave of good memories so Dave please keep them coming!
This is such a privilege to see someone like you make these vintage machines work. Can't wait to see what you do with it! Thanks for the great content!
Oh what great memories this brings back from my years at the DEC Ayr, Scotland manufacturing plant and the PDP 11/34 and so many other PDP 11 and Vax systems we produced on the FAST (Final Assembly and System Test) lines.. Cutting the CA1 to CB1 wire was needed for every DMA card the customer needed, so it became second nature after a while. I carried so much knowledge and experience into field service with me from manufacturing and it served me well. This is a great video along with the accompanying explanation of your issues and resolution. To get it all working is a fantastic achievement, well done.
I have enjoyed following your adventure on the PDP 11 Facebook group. I was fortunate to be a System Manager and programmer for an 11/34 and later 11/60 and 11/70 systems running RT-11 and RSTS/E. I too was nervous the first time I had to remove a grant jumper on the wire wrapped backplane to install a new disk controller card. Great times. Look forward to more videos bringing back more PDP memories.
I learned to program on a PDP-8. I worked on a project using 8080As, we used a cross assembler that ran on the PDP-8 loaded from paper tape. The original version didn't use the PDP-8's indirect addressing to use the additional memory in the box, so I wrote the code to put the entire symbol table in the additional RAM. When I went to UCSD, I got involved in the UCSD Pascal Project. They had ported the P-machine to the PDP-11s and were working on the Apple II port and various 8088 ports. I worked on the BIOS for the TRS-80 and drivers for 8-inch Cromemco drives. Watching you work on the PDP-11 brought back memories, especially the RK05s. One of the techs had the platter from one on the wall in his office - it was a big piece of metal.
I really enjoy your content. It is always educational in a way that most of us who have a little knowledge about the inner workings of computers easily can follow what is going on. Cheers from Sweden!
My first computers were (much smaller) salvaged from sidewalks waiting for the garbage truck in the 90’s. Always managed to get them running again! My first last printer was “destroyed” in a fire - I managed to get it printing again and used it for years. So while I have never used a mainframe or a “mini” this video made perfect sense to me. Very entertaining, Dave! I love your semi-sarcastic voice and dry sense of humor!
...Brilliant stuff there Dave, started off my computer education on these machines way back in the early 80's, had no clue about them (and still dont) but its great to see a lord like yaself taking the time to show us plebs what its all about.
This PDP 11 brings back a lot of memories. Back in the early eighties when I was still in high school up in the Sierra mountains on Friday nights and a couple friends would drive down to sac State University to the computer lab and get PDP 11 time and stay up till the wee hours of the morning. Really good memories with some really good friends. And the fact that the computer lab guys let us on the terminals was fantastic because we weren't even taking classes at sac state. Awesome video Dave as usual and yes I would love to see more videos around the PDP 11 or any of your vintage computers for that matter. Thank you as always
I am absolutely thrilled to see someone doing content on a relatively early PDP 11 that is capable of running ancient versions of Unix. I’ve been trying to wrap my head around the performance of these machines. But I see people say things like “they don’t have a clock”, which sounds more like legend than reality. I have a gut instinct that an early version of Unix could probably run on a Raspberry Pi Pico directly from flash. Either through emulation or cross assembly. I would love to see benchmarks compared to a 8MHz 68000. Since 68000 family was a very popular architecture for Unix in the 80s. A PC, both modern and vintage if possible. A 6502 @1.76 or 2.0 MHz because I suspect this will be closer than most people think to something like a PDP 11/20. Although it will depend heavily on the software algorithm due to the constraints of an 8bit architecture. And a Raspberry Pi pico. Preferably more than 1 algorithm. I’ve been trying to find performance data on early PDP 11’s relative to something people are familiar with.
I used to work on the 11/34 from 81 to 92. When you first started talking, I was screaming CA1 -CB1 at the screen LOL. I first completed the course on the 11/34 to gate level (hours of going through cct drawings page by page) I seem to remember it took a week to to the CPU cards alone. If you have any gaps int the DD11-PK (the first 9 slot backplane) then you have to have a bus grant card in slot D and can modify such cards turned 180 degrees and put in slot D to pass on DMA links. We also had major problems with the bus extender ribbons which were too long by far. Great content and much appreciate the video take me back to the years on when you could fix things with an extender card an step through the microcode with a logic probe and then replace the offending chip. The "Good" old days !!!
I once moved a PDP-11 to an upstairs office. It was only an 11/73, but it and its disk drives lived in a substantial 6-ft cabinet. Even with components removed, it took four of us to struggle up a steel staircase with the thing. It was only after we reached the top, when we were re-assembling it, that we discovered two massive lead bars (2-inch square cross-section) bolted in the base of the cabinet for stability.
I love your straightforward, detail-rich explanation. Great logical approach. As one somewhere on the spectrum (but lacking your emotional neutrality) I greatly admire your ability to overcome the many challenges that being on the spectrum presents.
