From mboxrd@z Thu Jan 1 00:00:00 1970 From: cdl@mpl.ucsd.edu (Carl Lowenstein) Date: Wed, 21 Aug 2002 12:59:42 -0700 (PDT) Subject: [pups] re: PDP-9 Message-ID: <200208211959.MAA04677@opihi.ucsd.edu> > To: pups at minnie.tuhs.org > From: Dennis Ritchie > Subject: [pups] re: PDP-9 > Date: Tue, 20 Aug 2002 23:55:55 -0400 > > Bilquist said (quoting Buitinck): > > > > we all know that UNIX first ran on the PDP-7 and then on the PDP-11/20, > > > but does anyone know anything about PDP-9 UNIX? it\'s mentioned in \"The > > > UNIX Time-Sharing System\" in the V7 manual: > > > > > > \"The earliest [version of UNIX] (circa 1969-70) ran on the Digital > > > Equipment Corporation PDP-7 and -9 computers.\" > > > Hmmm, I cannot exactly answer that, but the PDP-7 and PDP-9 were both > > 18-bit machines, and somewhat compatible, I believe. > > The whole line is (I believe): > > > PDP-4 -> PDP-7 -> PDP-9 -> PDP-15 > > > So I guess that if you had it running on a PDP-7, you could probably > > almost take the code unmodified and run it on the PDP-9. > > The PDP-15 have a different bus (Unibus?) I believe, and thus, > > peripherials are different from the predecessors. > > This obviosuly affects the OS. :-) > > The 7, 9, 15 were very compatible. I think the -15 > had some scheme for using an index register, which > the earlier ones didn't have, but it was otherwise > pretty much identical in IS architecture. > > There was very little rewriting to try Unix out > on the -9 and -15; perhaps just some tweaks in > the disk device commands. I don't think the > system actually ran on either for more than a few > hours. Ken was just playing around. > > The -15 may have had an electrically different > bus, but I'm reasonably sure it was not a Unibus. > All of them used IOT instructions, not memory-mapped > IO registers. > > Dennis What I remember, as the last gasp of PDP-15 production was a dual-processor setup, linked with a PDP-11. The intent was to take advantage of the lower-cost Unibus peripherals. I remember the sales literature, but do not recall ever seeing one. carl -- carl lowenstein marine physical lab u.c. san diego clowenst at ucsd.edu