Re: Seeking an explanation or theory

I agree, I do not have a problem. I am just curious as to why the
computer behaved as it did. Call me overly aggressive, but I like to
come away from a problem with an explanation to a solution. In most
cases when you find the solution you are able to understand why it
behaved as it did.

Something I have noticed repeatedly, with modern PCs having ACPI-aware
BIOSen and "soft" power supply switching, is the following:

- PC was shut down properly, unplugged, and serviced

- PC is plugged back into the wall

- There is an obvious surge of current - lights dim in the room for a
moment, fans start to spin, power LED comes on, etc.

- PC apparently shuts down, stops drawing power... fans stop, lights
go out, etc.

- Pressing the power-on button causes the motherboard and peripherals
to power up and boot.

In systems of this sort, the power-supply switch is "soft"... it's
actually just a logic signal to some circuitry on the motherboard,
which is powered by the PSU's low-current "standby" supply, and which
kicks the rest of the system awake. A similar kick can be provided by
the "wake on LAN" signal from the Ethernet adapter.

These motherboards also tend to have a BIOS setting which tells them
what to do when power is applied from a cold start: remain off, or
power up, or restore the previous power state.

I believe that the system design is such that if the motherboard is
powered down completely (i.e. no standby power available from the
PSU), it will automatically tug on the "power on, please!" line to the
PSU. Thus, when the PSU is plugged it, it'll immediately switch on
and provide full power to the motherboard, which goes through a full
reset, initializes the CPU, and starts up the BIOS.

The BIOS then presumably goes through some amount of its normal POST
processing, reads the system configuration out of NVRAM, and decides
whether it ought to power up. If so, it just continues with the boot.
If not, it configures the motherboard to generate another power-supply
wakeup event if the POWER button is pressed, and then switches off the
main power supply (leaving the standby supply running).

I can well believe that if there's a failure of some critical
early-stage step in the POST (including a failure to initialize the
DRAM controller or the DRAM itself), then the system might either just
stop dead in its tracks, or attempt another power-off/power-on cycle
to do a really *hard* reset of the failing hardware.

I suspect that's what you were seeing, if you plugged in some DRAM
that the motherboard "didn't like" for one reason or another.

--
Dave Platt <dplatt@xxxxxxxxxxxx> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
.

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