[Simh] Hardware fidelity in the VAX family simulators

[Johnny Billquist]

On 2015-07-08 23:39, Bob Supnik wrote:
> First, congratulations to Mark for running the current Ultrix 750
> problem to earth.
>
> Second, a brief diatribe about the need for fidelity to the hardware in
> the VAX simulators, which is (on the face of it) lacking outside the
> 3900 and 780 simulators.
>
> I have preached and documented the need for reasonable fidelity to
> hardware in implementing simulators. The papers on the SImH web site are
> filled with examples of minute details gumming up software behavior if a
> simulator gets them wrong. It looks to me like the 750, 730, 8600 are
> cut-and-paste jobs on the 780, and the MicroVAX I and II on the 3900. I
> admit there are strong family resemblances and, in some cases, reuse of
> hardware (the 8600 uses some of the 780 IO adapters), but as Ultrix
> proved, running VMS is an insufficient proof of correctness. Without
> reading (and implementing) the gory details of all the system-specific
> hardware, something is going to break. And if the goal is just to run
> VMS, why bother with variant models? The 780 and 3900 between them cover
> the complete history of VAX/VMS, Ultrix, and all the BSD variants.
>
> While the 750 now runs Ultrix, will it run the next OS it is given? Even
> with the current fix, there are multiple errors remaining in the UBA.
> The 730 won't boot Ultrix off the RB80; and so on.
>
> So my challenge to the community is twofold. First, is there more
> documentation on the variants available somewhere? I haven't found
> microcode sources or listings for the 750, 730, MicroVAX I, or 8600, for
> example. Second, are people prepared to "adopt" a model, read its
> documentation, and clean it up?
>
> End of diatribe.

I have certainly poked some at the 8600 in the past, which Mark knows. 
(And I have poked in the PDP-11/70 way way long ago, not sure if you 
even remember that one Bob).

As time allows, I'm happy to poke more at the machines I know. (Mainly 
those two I guess...)

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol