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.
/Bob
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