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What did I do to my PDP-8 today.

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    What did I do to my PDP-8 today.

    I am starting a thread which I hope others will post to detailing what they did to their PDP-8(s). I steal this idea shamelessly from forums in some of my other hobbies. Feel free to talk about anything you have been working on as long as it is PDP-8 related. Software, hardware, restoration, maintenance, I am interested in all of it and what others are doing. And if I am interested in what you are doing, I am almost certain others are as well.

    With that in mind I hope to see decent traffic here and I will follow up with my first post.

    Doug
    Doug Ingraham
    2nd owner of Straight 8 SN1173
    5 other PDP-8's including an 8/i and a DECSet 8000
    SOL-20

    #2
    Today finds me working on my recently acquired DECmate II. (Yes, it is a PDP-8.) Really!

    I have been collecting all the pieces to make a working machine and currently I am whitening the VR201 case by having it sit out in the sun. It has been exposed for several days so far and is quite a bit improved over the yellowish greenish color it had when I received it.

    Also on the VR201 I am soaking the face of the monitor in plain water in order to dissolve the PVA holding the protective glass to the face of the vacuum tube. This isn't the worst case of cataracts I have seen but it is the first time I have had to deal with it. I am going to give it a week or two and if it doesn't just fall off I will go to plan B. I don't know what plan B is yet.

    I dug out an old DOS machine, keyboard, monitor and hooked it up. Installed a 3.5 inch floppy as drive A: and a 5.25 inch 1.2 mb floppy as drive B:. Next problem was locating a version of DOS. I have hundreds of lbs of floppies but it is no longer in any kind of order. I eventually ran into a Win 95 boot disk which I remembered is sort of the last version of DOS. Plugged it in and it booted! YAY! You might be asking yourself why I needed a DOS machine and the answer is to run PUTR so I can burn some RX50 images to allow me to boot the DECmate. The next problem was how to get the data onto the 3.5 inch media. This turned out to be easier than I expected because while looking for a copy of DOS to boot I ran into a USB 3.5 inch drive (two of them actually) which I had never used. Got them from a friend years ago. Plugged it into my win 10 laptop and was able to look at the WIN 95 boot disk. Formatted a couple of 3.5 inch floppies and copied the PUTR files over to them and the image I needed. From this point it went like a champ. I will have to wait until I get a VR201 working to know if the DECmate can read it but PUTR seems to have no problems.

    I think that is enough for today. I hope you found this of interest. Looking forward to hearing what you are doing!

    Doug
    Doug Ingraham
    2nd owner of Straight 8 SN1173
    5 other PDP-8's including an 8/i and a DECSet 8000
    SOL-20

    Comment


      #3
      Ah, I really need to get back to my -8 Roguelike project...there was no way I was gonna have it ready for VCF West, but since that plan was cancelled due to the apocalypse anyway, I guess I've got another year to get it done
      Computers: Amiga 1200, DEC VAXStation 4000/60, DEC MicroPDP-11/73
      Synthesizers: Roland JX-10/SH-09/MT-32/D-50, Yamaha DX7-II/V50/TX7/TG33/FB-01, Korg MS-20 Mini/ARP Odyssey/DW-8000/X5DR, Ensoniq SQ-80, E-mu Proteus/2, Moog Satellite, Oberheim SEM
      "'Legacy code' often differs from its suggested alternative by actually working and scaling." - Bjarne Stroustrup

      Comment


        #4
        I too have a Decmate-II. Hard disk doens't work so it doesn't do much. The floppy drive in it seems to also have problems as it may click a few times but does not read. I'd like
        to be able to create images for it too, but have no old DOS PC anymore. I may have to swap a floppy drive from another DEC machine I have to see if that helps. I have never
        used a Decmate before. I prefer the blinken lights variety of 8, but sold my 8i and 8e long ago when I moved from Pa to NM. Best of luck to you.
        PDP-8 and PDP-11 enthusiast. But enjoy most older PC stuff too.

        Comment


          #5
          I got this particular DECmate II from Vince Slyngstad. We were able to verify that it would boot from floppy using one of the WPS (Word Processing System?) diskettes. We weren't able to make a copy of this boot disk at the time and didn't know why but I think I understand why now. We did several things wrong, wrong media and we had write protected the destination floppy. I took it all apart a couple of weeks ago and cleaned out all the grime. I 3D printed new feet for it as the original rubber feet were almost completely gone and I couldn't find anything even close to the right shape, size or materials. At the moment I have a monitor which is soaking in water, an untested keyboard, and an untested spare RX50 drive. The keyboard is in what I would class as very good condition cosmetically so I am hoping it will work. The drive popped up on an EBay search and was a reasonable price and I was lucky enough to win it uncontested. I have a lot of appropriate media and I would be happy to make some images for you once I know they work. From my research I discovered that you need to use a 1.2 mb drive to write the image but you do not use the quad density media. The RX50 makes use of only one side but uses the 96 tracks per inch ability of the high density drive. It writes that single side at lower bit rates. A really oddball format. It is a little surprising that a DOS PC even with special software can handle it.

          Doug
          Doug Ingraham
          2nd owner of Straight 8 SN1173
          5 other PDP-8's including an 8/i and a DECSet 8000
          SOL-20

          Comment


            #6
            Hi Doug, good to here from you. I find that the weather is still too warm for computer work. Most of my time has been spent on old cars. Have been working on a 1913 Model T roadster that came from Newton Iowa. Lots of fun. BUT......I have been collecting old FORTRAN IV books. I want to re learn FORTRAN. It was the first language I used back in the late 60's. I have the DEC version of FORTRAN IV and have worked out a few easy programs. In fact last winter, I found a bad transistor on my EAE boards. The FORTRAN square root function, which uses the EAE was giving wrong answers. I also cheat a little Simh goes a lot faster than the PDP8e and the teletype. Hope it's not too hot in South Dakota. Mike.

            Comment


              #7
              Hey Mike, long time no hear.

              I thought it was ‘T’ weather for you !

              It has been hot this side of the Pond recently as well. By the time we get AC installed the weather will change though!

              Dave

              Comment


                #8
                Hi Dave. Yup, it's been hot here also. And the humidity has been high. The old one two punch is getting harder to take on this old body. Here is a picture of the little beauty. I'm at the wheel. Mike
                SMALL1212.jpg

                Comment


                  #9
                  Nice.

                  But someone has put the steering wheel on the wrong side ...

                  Dave

                  Comment


                    #10
                    It's called, polarity. It depends on with side of the pond you are on. Sort of the right hand rule or something like that. Mike

                    Comment


                      #11
                      Hi Mike.

                      I am not familiar with the PDP 8/t variant of which you speak. Since the picture shows it being black it must have been some super secret project spawned deep in the Maynard skunkwerks. I am guessing it was some sort of autonomous vehicle control program in the 60's.

                      Simh and other emulators are a decent replacement as long as you run them on appropriate hardware. My own emulator should not be run on anything faster than an Intel 80386 33 mhz. Anything more modern than that is too fast. Simh is a little slower so it is probably ok to use one of the faster 80486 cpu's for that. I have estimated that modern servers are approximately 200000 times faster than the PDP-8 when using a single core.

                      On your EAE repair, did the EAE Maindecs help you diagnose the issue? I was looking at those a few years back and was struck by the way it was written. The author almost always does a CLA CMA followed by an AND to load the AC from memory instead of the usual TAD. The only reason I could think of for doing this was to avoid using the ADDer as much as possible. For the most part the EAE test would still work even with a somewhat broken adder. But of course you would never ever worry about the EAE not working if the ADDer was having issues.

                      Doug
                      Doug Ingraham
                      2nd owner of Straight 8 SN1173
                      5 other PDP-8's including an 8/i and a DECSet 8000
                      SOL-20

                      Comment


                        #12
                        This particular Model T is what is called a non electric car. There is no battery, just a magneto to power the ignition. Acytlene and oil power the lamps. So the PDP8 could fit in the car, but you would have to add some kind of power, maybe a wind turbine?

                        I use my Simh on my Windows 7 64 bit machine. I have seen no problems, in fact you are the first to mention such a thing. Now I have to go look.

                        Yes I used the MAINDEC as a starting place to trouble shoot the EAE. Do not remember exactly what the problem was, but i think it was some kind of division problem. I'd have to look at my notes to be sure. CRS is another problem with old humans. Mike

                        Comment


                          #13
                          Originally posted by Mike_Z View Post
                          This particular Model T is what is called a non electric car. There is no battery, just a magneto to power the ignition. Acytlene and oil power the lamps. So the PDP8 could fit in the car, but you would have to add some kind of power, maybe a wind turbine?

                          I use my Simh on my Windows 7 64 bit machine. I have seen no problems, in fact you are the first to mention such a thing. Now I have to go look.
                          A wind turbine would be interesting except for no power when not moving. In the DIYEV circles, mention of wind turbines is always followed by overunity issues the idea being you can charge the battery from the wind turbine while you drive down the road.

                          The only issue with using simh or other emulators is that they are too fast on computers faster than slow 486's or fast 386's.

                          Doug
                          Doug Ingraham
                          2nd owner of Straight 8 SN1173
                          5 other PDP-8's including an 8/i and a DECSet 8000
                          SOL-20

                          Comment


                            #14
                            I wish now that I had not recycled my old Linux box. It most likely had a 5.25 floppy drive. Or one could have been added. Anything I have now
                            doesn't have any way to plug in a floppy disk to a controller. I have many blank floppies and would gladly send a few if you could make me
                            a bootable image. I should try to floppy drice from one of my other DEC systems, as those work. It may be I have bootable media but the
                            floppy in the Decmate doesns't wish to read it.
                            PDP-8 and PDP-11 enthusiast. But enjoy most older PC stuff too.

                            Comment


                              #15
                              Originally posted by DougIngraham View Post
                              Feel free to talk about anything you have been working on as long as it is PDP-8 related. Software, hardware, restoration, maintenance, I am interested in all of it and what others are doing. And if I am interested in what you are doing, I am almost certain others are as well.
                              Really nice idea! It seems that there are a lot of people having fun with these machines
                              but don't post anything about it. Maybe because they think it is not special, maybe they
                              don't want to put much time to make a posting, or maybe don't want to show their collection...?

                              The last PDP8 thing I did is build another TTL VC8E clone so all my Omnibus machines have the
                              graphics (SpaceWar!) capabilities. Since a few weeks I have also a PDP11/10, so four bits extra... Oh dear...
                              Recently I got some PDP8 paper tapes with some music software. So I want to see if I can
                              make an interface for that so I can run the music program. Would be fun to have a good
                              sound quality instead of that horrible AM radio sound...

                              I don't know how often you check the forum here. I have made a few (too much?) topics which
                              are PDP8 related. When you check out my postings you will see quite a lot PDP8 related stuff...
                              I made some clone boards from several Omnibus boards. I have shared them all on my GitHub.

                              A computer using tubes would be high on the wish list. But even a small hybrid machine like the LGP30
                              is not really suitable to handle at home. So I have some Anita calculators which are hybrid with diode/Tube logic
                              and diode/tube/transistor logic. Really fun to have a calculator with over 200 tubes in it

                              My fun is restoring and developing hardware. My biggest wish is to have a discrete computer
                              like the Straight 8 or a PDP8/S. Just because the beauty of the technique with discrete transistors...

                              Regards, Roland
                              WTB: Case for Altair 8800 ...... Rolands Github projects

                              Comment

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