[TUHS] Re: 4.3 BSD version in the Unix Archive

[Michael Sokolov]

Markus Weber <jmbw at nather.com> wrote:

> Stand/copy from tms(0,1) to ra(0,1) fails with a 'disk unlabeled' diagnostic
> on a cold disk image.

It should print the unlabeled diagnostic, but then proceed rather than fail.  I
just double-checked the standalone driver source, and it does provide a default
label for RA82, as long as the MSCP controller actually returns RA82 as the MSCP
disk ID.  Does it give you an error message about disk type (some hex humber)
not supported?  If so, SIMH's MSCP emulation must be lacking in quality.

> If only ra0 is
> configured for simh, it takes the kernel a long time to decide that ra1,
> ra2, and ra3 are offline. Having said that, I do not know how long this
> takes on actual hardware.

On real HW it takes no noticeable time.

> the kernel (and
> not simh) subsequently segfaults (trap type 8, code = c0000200, pc =
> 8003fe16).

Well, obviously this doesn't happen on real HW, since on real HW it works (I'm
typing this message on a MicroVAX 3+ running 4.3BSD-Quasijarus).

But I will grant the possibility that the kernel is not w/o fault either in that
perhaps it's going south (dereferencing a garbage pointer and crashing) when the
MSCP controller (in this case SIMH's poor emulation) is doing something it
doesn't expect.  If this is so, it should be fixed, since even w/o emulators
(which I refuse to support on principle) real HW can be broken and return
garbage on reg reads, and the kernel must handle it gracefully.  I'll look into
it.

MS