[Simh] Can an emulated VAX survive a reboot of the host by save/restore ?

[Bucher Andreas]

Hi there, 

what's about the save/restore commands of SIMH ? I understood that it
can be used to store a full image if the emulators working memory and
emulated processor state (plus simh settings and all the rest ?!).

Then, it only would be necessary to notify simh of the host's shutdown
(and of course tell the host to wait until simh has finished), then shut
down and reboot. Is there any interface to send a running SIMH session
any comands like that ?

If simh starts up again, simply restore the saved dump file and the
system should be running as before (except for open network connections,
I assume).

Due to this, I tried an old idea of mine to have a VAX/VMS emulation
which (manually) survives the reboot of the host (and thus can also be
transferred to another host).

I just tried to save a test vax state (running on simh V3.6-1), then
exited and replaced simh by V3.7-1, mainly because of th idle feature
:-) Well, the VAX is idle but simh still draws 100% CPU, but that's a
different story.

After restart of simh, I executed my INI file (is this necessary, or is
everything stored in the dump file saved before ??), CTRL-E'd it during
system test, restored my dump, typed CONT and the VAX was up again ! OK,
it did a mount verification of DUA0: and I lost all open terminal
sessions, but the basic system itself was running.

Does anybody have any experience with that ?

Oh, I just noticed that I can only connect a terminal session to simh
console port (and of course to the IP addr. of the emulated VAX), but
not to the DZ board emulation, as it was possible before. It says
"Connected to the VAX simulator", but no login prompt - any idea ?

Or how about using it to create a "snapshot" of an emulated VAX and
later restore it (e.g. like in VMWare) ?

Andreas

> -----Original Message-----
> From: simh-bounces at trailing-edge.com 
> [mailto:simh-bounces at trailing-edge.com] On Behalf Of Davis Johnson
> Sent: Donnerstag, 21. Juni 2007 12:57
> To: Villy.Madsen at shaw.ca
> Cc: simh at trailing-edge.com
> Subject: Re: [Simh] Slow startup/shutdown...of the VMS simulator
> 
> Villy Madsen wrote:
> 
> >Does anyone have a suggesting for an existing device that I 
> could "misuse" -
> >just to get a one bit channel between the SCP and VMS ??
> >
> >Thanks
> >
> >Villy
> >
> >  
> >
> I don't know the VAX hardly at all, but some machines have a power 
> failure warning interrupt of some sort. Usually (in the real 
> hardware) 
> it doesn't give you enough time to do an OS shutdown. OS/32 
> (Interdata 
> 7/32, 8/32, Perkin-Elmer/Concurrent 3200) would save the processor 
> internal state to main memory. When power was restored the microcode 
> would kick a power restoration handler in the OS that would restore 
> processor state and continue execution.
> 
> Assuming an equivalent facility in the VAX and VMS you could possibly 
> have a VMS session that would survive a host OS reboot. You 
> would need 
> to save the memory image to disk, and restore it on restart.
> 
> Curses on you for sugesting somthing else that would be 
> interesting to do.
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