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Thread: PDP-8 wanted

  1. #21
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    Quote Originally Posted by djg View Post
    You sure? I checked mine and it's a 6120. Agrees with FAQ. I have a VT78 which uses the 6100. It's the one in the VT52 case. First DECmate is in VT100 case.

    http://www.faqs.org/faqs/dec-faq/pdp.../preamble.html
    No. I just took that info from Wikipedia. I should know better than just blindly trust that thing. Thanks for correcting me.

  2. #22
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    Sep 2020
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    Quote Originally Posted by DougIngraham View Post
    You should also add the PDP-8/m to your list. Although these didn't necessarily come with a front panel some of them did as it was an option. There are at least two more machines you should add to your list since they are just rebadged 8/e machines. They are the Lab-8 and the DECset 8000. The Lab-8 has dark green and light green switches and the DECset 8000 has dark and light blue switches with matching front panel graphics. There may be others but those are the ones that come to mind. The only 8/e in my collection is the DECset 8000. This machine was sold to newspapers to manage classified ads. The one I have is the only one I have ever seen. If someone does not know what they are selling these might not get advertised under PDP-8. You should also consider the PDP-8/a which is probably the most reliable. While the 8/a does not have a paddle switch front panel, it does have a front panel with 7 segment octal display and keypad entry. There was a glut of them a few years ago as they came out of active service in CNC machines. Another place to look for an 8/a is in electronics test gear as they were used in GENRad test equipment. Apparently some of these machines are still in service today. The GENRad machines have a 128k semiconductor memory board and a special board to allow for addressing the additional two bits. The 8/a could also be equipped with a floating point co-processor. The 128k memory and the floating point options are both pretty rare. My floating point board set does work but my 128k memory board does not. The 8/a normally has a hex wide CPU (M8315) but if you wanted an EAE they would replace the M8315 with the CPU set from an 8/e plus the two cards from the EAE. This would change a single slot CPU into a 6 slot CPU. The 8/e CPU is slightly faster as well. One of my 8/a's was equipped this way when in service as the accounting machine for a photo processing company.

    ...

    The 8/i is probably the easiest machine to maintain because it contains almost nothing but 7400 series TTL. This is mostly true for the 8/e omnibus machines but there are a few spots with parts that are difficult to source. The 8/a doesn't seem to need much repair but some of the boards are multilayer and have custom ROMs which makes them difficult as far as repair goes should something happen.

    Good luck with your search!
    Hi Doug,

    Thank you for all the info.
    From what I read the /M where OEM machines - many of them with their own front-panel - often almost identical to an 8/F except for the company name. One of these would be nice to have.
    The Lab-8/E appears to be essentially a PDP-8/E but with additional analogue boards for scientific use. I wonder how many of them where made.
    I have never heared of the DECset 8000. Google doesn't give you any useful hits about what this machine is other than a "Review" which lacks details. Ebay comes up empty handed too.
    The 8/I scares me because of its weight and the complexity of the wire-wrap back panel, but is otherwise a very desirable machine.

    Thanks again and best regards
    Tom Hunter

  3. #23
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    Quote Originally Posted by thunter0512 View Post
    Hi Doug,

    Thank you for all the info.
    From what I read the /M where OEM machines - many of them with their own front-panel - often almost identical to an 8/F except for the company name. One of these would be nice to have.
    The Lab-8/E appears to be essentially a PDP-8/E but with additional analogue boards for scientific use. I wonder how many of them where made.
    I have never heared of the DECset 8000. Google doesn't give you any useful hits about what this machine is other than a "Review" which lacks details. Ebay comes up empty handed too.
    The 8/I scares me because of its weight and the complexity of the wire-wrap back panel, but is otherwise a very desirable machine.

    Thanks again and best regards
    Tom Hunter
    I have both an 8/m and an 8/f, and they are pretty much identical, except for the "8/m" vs. "8/f" lettering on the front (obviously).
    Yes, the 8/m was the OEM model, but obviously at least some of them never had any company specific panels.

  4. #24

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    Quote Originally Posted by thunter0512 View Post
    What I meant was only a small number of the "Spare Time Gizmos" SBC/FP/IOB-6120 kits were made. This kit was implemented using the Harris 6120 CPU chip.
    There is also the RetroBrew Computers SBC6120-RBC Edition version of the "Spare Time Gizmos" SBC6120 - this is easy for folk to get, if they don't mind constructing it or know someone who will do it for them, as the Gerber files are available online and it is very affordable these days to get PCBs produced (which is what I have done). The processor and other "rare" parts also seems to be readily available (I have ended up with a couple of sets: it is nice to have spares). The IOB6120 can also be built the same way, although assembly is a little harder than the SBC6120. The IOB6120 is not absolutely necessary for a working system; the SBC6120 can be used on its own. The FP6120 (the STG front panel) is a different matter as the Gerber files did not seem to be available anywhere - so at the moment one of my hobby projects is looking at reworking that, including making it to be the same size (face on) as the "Planned Obsolesce" Raspberry Pi PiDP-8/I and PiDP-11/70. I need more spare time .

    In regards to "actual" PDP-8s: I regularly check for them and have done so for some time. I suspect many systems are being broken up and sold as parts at very high prices - the sellers of parts seem to be happy to wait for them to sell (if they ever do)?

  5. #25
    Join Date
    Sep 2020
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    Perth in Western Australia
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    Quote Originally Posted by kb811 View Post
    There is also the RetroBrew Computers SBC6120-RBC Edition version of the "Spare Time Gizmos" SBC6120 - this is easy for folk to get, if they don't mind constructing it or know someone who will do it for them, as the Gerber files are available online and it is very affordable these days to get PCBs produced (which is what I have done). The processor and other "rare" parts also seems to be readily available (I have ended up with a couple of sets: it is nice to have spares). The IOB6120 can also be built the same way, although assembly is a little harder than the SBC6120. The IOB6120 is not absolutely necessary for a working system; the SBC6120 can be used on its own. The FP6120 (the STG front panel) is a different matter as the Gerber files did not seem to be available anywhere - so at the moment one of my hobby projects is looking at reworking that, including making it to be the same size (face on) as the "Planned Obsolesce" Raspberry Pi PiDP-8/I and PiDP-11/70. I need more spare time .

    In regards to "actual" PDP-8s: I regularly check for them and have done so for some time. I suspect many systems are being broken up and sold as parts at very high prices - the sellers of parts seem to be happy to wait for them to sell (if they ever do)?
    A copy of the SBC6120 board set including the FP6120 PCB is available on Ebay: https://www.ebay.com/itm/164540234434

    The Russian seller has his own website with the boards at: https://chipkin.ru/product/pechatnye-platy-dec-pdp-8-e/

    I have ordered it and once I receive the PCBs I will report about the quality.

    Best regards

    Tom Hunter

  6. #26

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    Quote Originally Posted by kb811 View Post
    The IOB6120 can also be built the same way, although assembly is a little harder than the SBC6120. The IOB6120 is not absolutely necessary for a working system; the SBC6120 can be used on its own. The FP6120 (the STG front panel) is a different matter as the Gerber files did not seem to be available anywhere - so at the moment one of my hobby projects is looking at reworking that, including making it to be the same size (face on) as the "Planned Obsolesce" Raspberry Pi PiDP-8/I and PiDP-11/70. I need more spare time .
    I have IOB parts and PCBs here, though I've not invested the time to kit them up.

    I also have made a start on FP6120 drawings in the boards collection on my site, www.so-much-stuff.com. (I suppose with some arm twisting I could be convinced to finish drawing the traces.)

    Vince

  7. #27
    Join Date
    Sep 2020
    Location
    Perth in Western Australia
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    Quote Originally Posted by kb811 View Post
    There is also the RetroBrew Computers SBC6120-RBC Edition version of the "Spare Time Gizmos" SBC6120 - this is easy for folk to get, if they don't mind constructing it or know someone who will do it for them, as the Gerber files are available online and it is very affordable these days to get PCBs produced (which is what I have done). The processor and other "rare" parts also seems to be readily available (I have ended up with a couple of sets: it is nice to have spares). The IOB6120 can also be built the same way, although assembly is a little harder than the SBC6120. The IOB6120 is not absolutely necessary for a working system; the SBC6120 can be used on its own. The FP6120 (the STG front panel) is a different matter as the Gerber files did not seem to be available anywhere - so at the moment one of my hobby projects is looking at reworking that, including making it to be the same size (face on) as the "Planned Obsolesce" Raspberry Pi PiDP-8/I and PiDP-11/70. I need more spare time .

    In regards to "actual" PDP-8s: I regularly check for them and have done so for some time. I suspect many systems are being broken up and sold as parts at very high prices - the sellers of parts seem to be happy to wait for them to sell (if they ever do)?
    Encouraged by another successful PCB order yesterday using PCBway I have now ordered 5 "RetroBrew Computers SBC6120-RBC Edition" PCBs from JLCPCB which you used. It will be interesting to compare the quality of the PCBs from these two manufacturers. For the same gerbers the PCBway quote was a bit more expensive. I will use the Russian front-panel PCB and the RetroBrew SBC-6120 to build the complete system.
    Cheers
    Tom

  8. #28
    Join Date
    Jun 2019
    Location
    Manitoba, Canada
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    6

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    Hi Tom, I have a PDP-8/m in very good condition with a lot of original documentation and a couple of extra boards. If you are interested I will grab a couple of pictures when the kids are down. Let me know if you want more information.

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