Can anybody elaborate more on what the VMS power failure options are??
OPC$CRASH sure looks like a crash, but what happens before the belly up?
Some time ago (at least a decade), I started looking at re-enabling the
Tops-20's power failure code with an eye towards making some changes to
the KLH10 micro-engine.? So clearly, at a minimum, I would have needed
to catch a SIGPWR and then do something useful with it, which then meant
some nosing around in APRSRV and SCHED and some other monitor code.
At one point, Tops-20 appears to actually have been able to save what it
was doing and cleanly resume on power up; in other words, not crash.?
Some hardware was able to detect a power fail and cause an APR generated
PI.? Any running process was dismissed, the front end was notified and
any disk I/O was completed.? The caches were shut off.? That leaves the
volatile structures.? Assuming you were running with core (MA20's), you
could survive the power outage.? A power on would generate an interrupt
which checked whether the power off handling was completed.? If so, away
you went.
I don't ever remember ever that working at Columbia, which stands to
reason since we were running semi-conductor memory. We only had a single
MA20 to increase the total memory of one particular system to 3.75 MW
(the rest was MF20).
However, the code itself is still there.? Fully supporting the power
fail would have then involved the 20 signaling the micro-engine (perhaps
by doing a CONO to the Idler device with a magic bit set), that it was
done.? KLH10 would then have had save about 34 MB of memory and exit.
It wasn't clear what volatile structures in the micro-engine needed to
be preserved, so I stopped there and turned to other things.? If the
host operating supported sleep, maybe not much. You can't just 'sleep'
Tops-20 because on resumption, the keep-alive counters won't have been
updated and it will immediately crash.?? It has to know the power went out.
If you don't have a UPS, you may not have a lot of time to do things.?
Depending on the power supply and capacitor usage and discharge, you
might have only milliseconds.? I would imagine that's plenty for SSD
storage, it might not be enough for rotating media.
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On 5/30/20 1:14 PM, Supratim Sanyal wrote:
Good afternoon everyone,
What are you guys doing to get something like OPC$CRASH invoked when a
UPS signals it is on battery?
I have serial connectivity to TTAx ports on a Microvax 3100-80 running
OVMS 7.3. Recommendations on a UPS?
Generally how do you get a VAX to shut down immediately on UPS going
on battery?
Thanks in advance
Supratim
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Supratim Sanyal, W1XMT
39.19151 N, 77.23432 W
QCOCAL::SANYAL via HECnet <http://www.update.uu.se/~bqt/hecnet.html>