[rescue] Perverse Question

Dave McGuire mcguire at neurotica.com
Sat Jun 7 18:59:29 CDT 2003

On Saturday, June 7, 2003, at 07:51 PM, Michael Free wrote:
> If I remember right, in classic terms (XT, the last time I dealt with 
> it)
> "SENS" or "Power Good" is an input.... the motherboard can tell the 
> power
> supply if the power is good. You can route this to ground (iirc) with a
> momentary switch for a reset button, something the IBM PC and XT was 
> sorely
> lacking.
> Luckily they had a little removable panel in the back which made 
> drilling a
> hole for the switch much, much easier :)

   Actually the "Power Good" signal is an output from the power supply.  
On better supplies it's a logical AND of the output of a group of 
window comparators which check that each output voltage is within 
tolerance.  On cheaper supplies (and all modern PC supplies that I've 
seen) it's simply a signal that goes active after a short delay 
following powerup.  It is the intention that the processor not start up 
until that signal is asserted.


Dave McGuire             "I've grown hair again, just
St. Petersburg, FL           for the occasion."       -Doc Shipley

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