[Simh] Booting the vax750 simulator.

[Ethan Dicks]

On Tue, Jun 23, 2015 at 7:06 PM, Henry Bent <hbent at oberlin.edu> wrote:
> Out of curiosity I tried Ultrix 4.3 and 4.5 on the /750, both with genvmunix
> and a custom kernel, and both showed the problem.  Whatever the issue here
> is, it appears to never have been fixed.  I tried disabling just about every
> device I could save for the disk, and I still got a panic every time.  The
> only thing I haven't yet tried is using a different disk controller (than
> the UDA50).

Definitely try a different disk.  UNIX device drivers do not use the
hardware the same way that VMS drivers do.  I helped debug the Simh
RP03 driver long ago because it wouldn't fully boot 2.9BSD (long story
short is that it was because the BSD driver wrote to a read-only
register to initiate an interrupt for device probing).  I've also run
into issues with 4.3BSD not booting an 11/730 with RB80 (I did narrow
it down to specific lines of code in the rb.c driver but haven't
figured out what's not happening right.  It's *very* early in the boot
sequence that things go off the rails, so it wasn't too hard to trace
in the code).

> Interestingly, Ultrix 4.0 will boot on a /730 if you make a custom kernel
> (genvmunix is too big).  I didint' try 4.3 or 4.5.

Huh.  I haven't tried that.  Interesting.  Which disk?  UDA50 or the
IDC + RB80?  (DU driver vs DQ driver in VMS terms)

-ethan