>Uhhmmmmmm... would you want to take a stab at explaining why
>the following happens on my system?
>
>I perform a proper windows shutdown -- with NO errors or problems,
> turn off the power, count to five and turn it back on.
>49 out of 50 times I will *immediately* see a scrambled video
>display and the PC will not boot.
>
>But if I turn of the pc (as above) and wait 20-30 seconds,
>it boots correctly.

I guess (and it is a guess) that in the old days when there was
a lot of power-hungry TTL in computer systems, the power supply
collapsed pretty quickly to near zero volts when the juice was
switched off. There would have been lots of conducting p-n
junctions and many resistive paths through bias networks.

Nowadays, most of the logic is in a few VLSI CMOS chips.
These have conductive FET channels, not junctions.
Voltage thresholds are engineered into the physics of
the semiconductor material and the gate geometry, not
determined by potential dividers or bias chains.

As a result, when you pull the plug the PSU voltage collapses
rapidly until the conduction threshold of the CMOS gates is
reached, but then the current flow is reduced by several
orders of magnitude and the voltage decline is _much_
more gradual. You might try hanging an analogue high-resistance
voltmeter on the 5V line - the effect should be visible.

I guess (and now I am hanging on a limb) that 5 seconds
is not _quite_ enough for some reset-generating circuitry
to discharge to a voltage at which it itself resets,
and 20 seconds is enough.

Len Warner <[log in to unmask]> WWW Pager http://wwp.mirabilis.com/10120933