JeffCA said:
I just installed a new A7V400-MX power MB for somebody and they are
having problems with the power. Basically she says that after the
computer has been off for several hours she has to unplug and plug in
the power supply for the computer to turn on. She said it turns on
fine if it's only been off for a short period of time. My guess is
it's the power supply, but does anybody have any other ideas or
experience with this problem? I've read quite a few posts about A7V's
having power problems or BIOS issues. Any ideas?
There have been other motherboards with "cold boot" problems.
One person observed that the room temperature made a difference.
Another theory tested the possibility that there was a leakage
current coming down the monitor cable. Disconnecting the monitor
cable, then attempting to turn on the machine, might make it start
OK (which really isn't a lot of help to the end user).
I've never really read either a reasonable explanation for what
is going on, or read of a real good workaround. I know it is
possible for the digital logic running in the CMOS section of
the Southbridge, to be temperature sensitive (i.e. a design
fault). But how many companies will publically admit to a
design fault like that ?
It could be, for example, that +5VSB is being overloaded while
the computer is sitting there, waiting for the user to press the
power button. You could set the USBPWR headers to +5V, instead
of +5VSB, disable Wake On LAN (so the ethernet chip runs in a
lower power state, when the computer is off). Using a
clamp-on DC ammeter would allow you to verify whether the
sleeping or active computer is drawing too much current.
Or, you could experiment with another power supply. Depending
on the speed of S462 processor you are using, I'd want a power
supply with a 5V output rated for 20A to 25A. I've measured
17A consumption on my 3200+ while running Prime95, and by the
time you throw in 1A per disk drive, and 5.5A for an ATI9800pro
video card power cable (under gaming conditions), you are up
around 25A. The other rails should be less demanding, and even
a crappy 12V @ 10A rating would be enough. The power supply
rating doesn't have to be that high - an Antec Truepower 330W
offers 5V@30A.
Paul
