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Rev

Were core-based computers typically designed so that after an unexpected power failure they could (when power was re-applied) resume operation where they left off? My conjecture would be that if one performed a "shutdown" procedure one could have a system save everything of interest into core and then start executing NOPs until power was removed; if one used the proper procedure when restarting, one could then restore the system state. Do you know if systems typically had a means of autonomously triggering a shutdown procedure if external power was lost? If a core-based system were...
– supercat
Commented Nov 2, 2014 at 16:08
...to cease functioning due to power failure and didn't get a chance to finish up any operations that were in progress before power was lost completely, I would expect that whatever unit of memory was being acted upon would be lost; further, since I would expect that program counters, sequencers, etc. would not be kept in core memory, the contents of those would be lost as well.
– supercat
Commented Nov 2, 2014 at 16:12
@supercat - There were a wide variety of designs. Mainly the effort centered around maintaining the integrity of the file system, so crash recovery was most likely to try to find file operations that were in progress and complete those. But I'm remembering that it was fairly common to detect a power failure and stash the CPU registers.
– Daniel R Hicks
Commented Nov 2, 2014 at 19:33
If the memory is being used as a file system, I would expect that code could ensure that it would always be a in a valid state, such that any interrupted operation could be either rolled back or run to completion. On the other hand, by my understanding core memory was often used not because it was non-volatile, but rather because it was cheaper than any alternatives, so I'm curious to what extent designers took advantage of non-volatility or just ignored it.
– supercat
Commented Nov 2, 2014 at 19:37
@supercat - They took advantage of it quite often (and hence, eg, file systems were less robust than one would have liked for volatile RAM). Not that it was a big "selling point", but it was there, so why not?
– Daniel R Hicks
Commented Nov 2, 2014 at 19:43

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