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Found some photos of the SC-40 deal at bitsavers. https://bitsavers.org/pdf/compuserve/ https://bitsavers.org/pdf/compuserve/ Ooh, and these SC-40s have compu

by imglorp 18d ago

Found some photos of the SC-40 deal at bitsavers. https://bitsavers.org/pdf/compuserve/ https://bitsavers.org/pdf/compuserve/ Ooh, and these SC-40s have compuserve tags and a stack of disks! I hope someone preserved the data. https://onlineonly.christies.com/s/firsts-history-computing-paul-g-allen-collection/systems-concepts-sc40-pdp-10-clone-149/230087 https://onlineonly.christies.com/s/firsts-history-computing-...

p_l 17d ago
AFAIK SC-40 were all made for CompuServe, and effectively by CompuServe
- FrankWilhoit 17d ago
  Systems Concepts may have had other prospects, but they had so much trouble getting the product out the door that Compuserve ultimately helped them finish it, licensed it (? exclusively), and produced all but a couple of the machines that went into production. I found a microcode bug in one of the first SC-built machines that caused the string-comparison instruction to return true whether or not; Gary Brown took that to SC and reported their reaction as "Damn, you caught us!", and that was kind of the end of that. You might have some stories to tell of the flight from X.25...?
  - p_l 17d ago
    I am from a place where CompuServe was just something you read about the way you read travelogues or otherwise reports from far away country, unfortunately. I encountered data about System Concepts due to being interested in PDP-10 history and so on.
    - FrankWilhoit 17d ago
      Profound apologies -- on the basis of one of your earlier comments, I took you for someone with the same initials.
  - imglorp 17d ago
    Was the whole SC endeavor to avoid buying PDP-10s?
    - FrankWilhoit 17d ago
      DEC quit making them in 1983.
      - imglorp 16d ago
        Then VAX would have been an option, especially since there were migration tools from PDP. And VAXen cluster for scaling.
        p_l 16d ago
        There were options for migrating from PDP-11, not PDP-10. PDP-11 was a 16bit byte-addressable minicomputer that was extended to 22 bit physical addresses through MMU. VAX took PDP-11 and extended it into 32bit flat addressable paged system. PDP-10 was 36-bit, word-addressed with 18bit addressing (plus segment extensions in KL-B that were only really implemented in 3rd party follow-ons, a mainframe-in-all-but-name. VAX would mean starting from zero unless nearly everything was written very high-level, which is doubtful given the optimizations needed to run so many simultaneous users.
        FrankWilhoit 16d ago
        It had more to do with the ecosystems and the corporate relationship. The -10s came from a earlier perspective. It was open source before "open source". You bought the software and you got the source, because of course you did, you couldn't even install it otherwise. Compuserve tracked TOPS-10 up to version 6.01, with their own additions and patches: far-reaching but well encapsulated. They could not track 6.03, so they "forked" it, to use the modern word. The question of support was always fraught. Compuserve offered all of their changes to DEC, who mostly sniffed at them. But from DEC's perspective, one of the major purposes of the VAX platform was to lock all that kind of thing down and go to a support model more like that of IBM.

by imglorp 18d ago

p_l 17d ago

AFAIK SC-40 were all made for CompuServe, and effectively by CompuServe

FrankWilhoit 17d ago
Systems Concepts may have had other prospects, but they had so much trouble getting the product out the door that Compuserve ultimately helped them finish it, licensed it (? exclusively), and produced all but a couple of the machines that went into production. I found a microcode bug in one of the first SC-built machines that caused the string-comparison instruction to return true whether or not; Gary Brown took that to SC and reported their reaction as "Damn, you caught us!", and that was kind of the end of that. You might have some stories to tell of the flight from X.25...?
- p_l 17d ago
  I am from a place where CompuServe was just something you read about the way you read travelogues or otherwise reports from far away country, unfortunately. I encountered data about System Concepts due to being interested in PDP-10 history and so on.
  - FrankWilhoit 17d ago
    Profound apologies -- on the basis of one of your earlier comments, I took you for someone with the same initials.
- imglorp 17d ago
  Was the whole SC endeavor to avoid buying PDP-10s?
  - FrankWilhoit 17d ago
    DEC quit making them in 1983.
    - imglorp 16d ago
      Then VAX would have been an option, especially since there were migration tools from PDP. And VAXen cluster for scaling.
      - p_l 16d ago
        There were options for migrating from PDP-11, not PDP-10. PDP-11 was a 16bit byte-addressable minicomputer that was extended to 22 bit physical addresses through MMU. VAX took PDP-11 and extended it into 32bit flat addressable paged system. PDP-10 was 36-bit, word-addressed with 18bit addressing (plus segment extensions in KL-B that were only really implemented in 3rd party follow-ons, a mainframe-in-all-but-name. VAX would mean starting from zero unless nearly everything was written very high-level, which is doubtful given the optimizations needed to run so many simultaneous users.
        FrankWilhoit 16d ago
        It had more to do with the ecosystems and the corporate relationship. The -10s came from a earlier perspective. It was open source before "open source". You bought the software and you got the source, because of course you did, you couldn't even install it otherwise. Compuserve tracked TOPS-10 up to version 6.01, with their own additions and patches: far-reaching but well encapsulated. They could not track 6.03, so they "forked" it, to use the modern word. The question of support was always fraught. Compuserve offered all of their changes to DEC, who mostly sniffed at them. But from DEC's perspective, one of the major purposes of the VAX platform was to lock all that kind of thing down and go to a support model more like that of IBM.