For sale 128K Core RAM Industrial PDP 11/40 Massbus System

Noel Chiappa jnc at
Mon Oct 31 08:36:12 CDT 2016

    > From: Ed Sharpe

    > was Unix or C the one developed on the 11/20?

Both. Unix Version 1 was written in PDP-11 assembler, for the -11/20;
although that was a re-write of an earlier version written in PDP-7
assembler. C was developed from B in good part because the word address model
of B (inherited from its ancestor BCPL) wasn't a good match for the PDP-11's
byte addressing model. More here:

    > From: Christian Corti

    > I think the IP stack needs separate I/D and more memory

I read that the networking code in 2.x uses Supervisor mode (apparently it
needed more address space than was available with only kernel, even with
split I/D).


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