> On Mar 23, 2020, at 10:03 AM, Robert Armstrong <b...@jfcl.com> wrote:
>
>> Paul Koning <paulkon...@comcast.net> wrote:
>> ... extended microcode to run PDP-8 code faster. But it was an 11/60
> running RSTS/E.
>
> So it is true (well, sort of, but with a PDP-11/60 rather than a
> VAX-11/730)?? Do you know any details of how it was implemented? If it ran
> RSTS then it was obviously still a PDP-11 at the same time it was emulating
> a PDP-8. Was there a -8 "compatibility" mode, something like the -11 mode
> on the VAX?
RSTS/E had a general mechanism called "run-time system", vaguely like a cross
between a shell and a shared library. The earliest officially released one
(other than BASIC) was the RT11 runtime system, which provides RT11 system call
emulation (SJ subset) and a simple V2-style command line interface. This was
done to allow Sysgen to be run on RSTS, starting with V5B. Later RSX emulation
was added via the RSX runtime system, which eventually migrated into the kernel.
Runtime systems can also implement languages or the like; BASIC, TECO, FORTH,
and ALGOL are runtime systems and basicaly implement virtual machines for the
language in question.
I think that the PDP-8 emulation was done as a runtime system, with WCS
microcode to help execute the instructions faster than they could have been
emulated in PDP-11 code. I'm fairly sure that Richie Lary, one of the most
famous PDP-8 developers in DEC, did much of the work, and presumably the
microcode in particular.
paul
_______________________________________________
Simh mailing list
Simh@trailing-edge.com
http://mailman.trailing-edge.com/mailman/listinfo/simh
