RE: Diskless MicroVAX II boot crash in simh current

[Mark Pizzolato - Info Comm <Mark%infocomm.com@localhost>]

On Thursday, December 28, 2023 at 6:50 AM, Mouse wrote:
> > > boot -s
> > Trying BOOTP
> > Using IP address: 10.9.10.24
> > myip:  (10.9.10.24)
> > root addr=10.9.10.192 
> > path=/Data/Code/vax/NetBSD-10.0_RC1/rasterloop-10.0_RC1
> > stray interrupt: vector 0x18, ipl 31
> > stray interrupt: vector 0x18, ipl 31
> > stray interrupt: vector 0x18, ipl 31
>
> Vector 0x18 is, to quote the VARM,
>
>         18     reserved operand                       fault or abort  0
>
> Either the kernel loaded is corrupt or simh fails to correctly implement some 
> relevant instruction; I don't see any other alternatives.
>
> > Any suggestions?  Since my real KA630 boots fine with this config, 
> > should I follow-up with the simh team?
>
> I'm hardly authoritative, but I'd be inclined to say yes; if software behaves 
> differently on the real thing and the emulation, it obviously is an imperfect 
> emulation.  (This can be a feature rather than a bug, such as the various 
> idle-loop hacks emulators do, or the way emulation can sometimes be faster
> than the real thing.  I have trouble seeing the symptom you give as such a case.)

I agree with this assessment.

The setup to reproduce the above failure seems rather complicated or I'd offer to dig a little:

1) A MOP server on the LAN to download that then accepts the "boot -s" command 
2) Another system (maybe the same at IP address 10.9.10.192) that actually delivers the data being loaded from /Data/Code/vax/NetBSD-10.0_RC1/rasterloop-10.0_RC1

The wire protocol for the second step might not well tolerate the potentially different timing in the packet delivery (and possible overrun) activities that may be happening in simulation.  The lack of messages before the reserved operand faults suggests that they might be happening during the kernel loading (in the loader) OR during the actual early stage kernel startup...

Some things which can affect XQ timing might be:

    SET XQ THROTTLE 
    SET XQ POLL

See sim> HELP XQ SET

- Mark


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