H7874 power supply

Jon Elson elson at pico-systems.com
Mon Mar 30 13:37:09 CDT 2020

On 03/30/2020 11:49 AM, Paul Koning via cctalk wrote:
> Thise signals don't seem like a problem: just hardwire them to the desired logic level.  PDP-11s need a real functioning DCOK signal iff you want to do power fail interrupt handling, otherwise they don't.  Do VAXen have power fail interrupt?  If yes, does anyone actually use it?
The VAX 11/780 absolutely had power fail, and it DID work.  
You could just walk up to the CPU and turn the key to 
standby, and it would power down everything but the memory.  
When you turned the key back to on, it would power up, load 
microcode and resume the paused system image VERY smoothly.
You could also power down the Unibus box, and it would 
recover all the devices and resume
when you turned it back on.
Anything tasks that ran off Massbus peripherals could keep 
running while the Unibus was off.
I did this quite often while swapping I/O devices and such 
after device drivers became loadable.


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