Two Stop Bits | Some random thoughts. Writing a timesharing system for a computer with a 16-bit...

larsbrinkhoff 1 day ago | parent

Some random thoughts. Writing a timesharing system for a computer with a 16-bit address space forced the Unix philosophy with many small single-purpose programs passing data between them. A timesharing system on a PDP-10 wouldn't have this constraint, and may well not have developed the Unix philosophy. Maybe that would have removed some of the appeal of "Unix-10".

Second, the VAX grew from the PDP-11 as a 32-bit addressing extension. So porting from the PDP-11 to the VAX is rather natural and easy. In contrast, the PDP-10 is rather different from both the PDP-11 and VAX. Programs written in assembly language will not port over. If Bell labs would have developed a C language for the PDP-10, I wager it would have looked different and not have become popular in an 8-bit byte world.

bmonkey325 1 day ago
Some forget that Unix started out on the pdp-7 which was 18-bit words so in some ways the architecture argument doesn’t really hold up. I think it’s more what machine were they could access.
https://linfo.org/pdp-7.html#:~:text=The%20PDP-7%20was%20a%2....
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- larsbrinkhoff 20 hours ago
  PDP-7 Unix is even more cramped with a 12-bit address space per process.
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  - bmonkey325 16 hours ago
    This version of Unix was all assembly code and not portable. Once they could move to a better machine I think they realized they didn’t want to write it again in assembly because porting could be difficult.
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    - larsbrinkhoff 14 hours ago
      My argument is that the PDP-7 and PDP-11 possibly forced the Unix philosophy. I don't understand what you are arguing.
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- KODust 1 day ago
  Yes, this is the thing -- it's clear that Ken Thompson valued simplicity, one reason being that he and a couple of other people could maintain the entire thing without a large support organization. Whether that would have survived the PDP-10, I'm not sure. But I suspect it would have have been recognizably Unix.
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