H7874 power supply

Robert Armstrong bob at jfcl.com
Tue Mar 31 12:19:33 CDT 2020

> Jon Elson <elson at pico-systems.com> wrote:
>The VAX 11/780 absolutely had power fail, and it DID work.  

  So did the 11/730 and I imagine the 750 as well.  No core, but there was a
battery backup option to keep main memory alive and refreshed even in the
event of power failure.

>I did this quite often while swapping I/O devices and such 
>after device drivers became loadable.

  It was (is!) quite handy on the 730 as well.  If your configuration has a
separate BA11-K for the UNIBUS peripherals, then you can power down that box
without turning off the CPU.  It took 20-25 minutes to boot up the 730 from
a dead start, so this was a great time saver.


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