Thanx for your time and patience.
In review,
I have a HP Pavilion m8530f Media Center computer given to me free. It
is shown at
http://h10025.www1.hp.com/ewfrf/wc/...&cc=us&dlc=en&lc=en&jumpid=reg_R1002_USEN#N79
Its MOBO is a M2N78-LA shown at
http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&docname=c01925562
The system has one 750GB hard drive and one DVD burner.
There are no recovery disk(s) or manuals. It has VISTA installed on
it with a few apps. It does have the usual recovery partition on the
hard drive.
I was told that the system would not start up at all. I thought I
could resurrect this system with a few hardware replacements maybe and
have a pretty good system. Maybe not? Anyway, my intent is to
replace VISTA with XP (SP3).
I find that when I boot up the system after sitting cold for a long
while, the BIOS recognizes all hardwares, and even brings up the VISTA
desktop. But, when I do the same a second or third time, after the
system seemingly is a little 'warm', no hardwares are detected and the
system will not boot up at all.
I find that the M2N78-LA mobo does not have a IDE (PATA) capability,
so I thought to replace that mobo with a GIGABYTE GA-MA785GM-US2H
or a BIOSTAR TA780GM2. I thought this would give me a pretty good
result. Maybe not?
When you say, "a second or a third time", then you've seen success on a
second reboot ? That's an important observation, because some computers
are "broken on a warm boot", meaning the second reboot fails consistently.
If you're making it to a third reboot, and then it fails, it might be
something simple, like the Southbridge heatsink not being in contact
with the chip, and the chip is overheating.
Now, if that was a viable theory, that it's overheating, then perhaps
you'd see the "hard drive disappear" while the system is running, and
then it would crash on a hard drive error ?
Find a hardware monitoring utility, and watch the listed temperatures.
There is no guarantee that an application like this, is accurately reading
temperatures, but you can give it a try. The chip may have a thermal
diode, wired to the hardware monitor interface.
http://www.almico.com/speedfan442.exe
Heatsinks have all manner of fasteners on them. The hook and wire method,
is fine, until a hook pulls out of the motherboard, and that can leave
the heatsink dangling. If you take the heatsink off for inspection,
then the chip underneath may be using a "bare die", rather than having
a heat spreader lid on it. You have to be careful not to tilt the heatsink
when putting it back on (for fear it will crack an edge of the silicon).
Some chips use rubber bumpers stuck on the corners of the chip, to
equalize the spacing. Or they could use a sil pad, instead of thermal
paste, and so on. You can't smear a replacement thermal paste
everywhere, because there may be some surface mount components up there
(resistors and caps), and only the silicon die area should have paste on it.
Some of our designs at work, used a kind of silicone rubber thermal
conductor, which was a space filling solution. But the thermal
performance of such solutions, is worse than thermal paste. The thermal
paste also requires slightly less "normal force" or pressing down force,
to make the paste work well.
If a hook and spring scheme has pulled loose, you'll have fun putting it
back. A hook on a board I have here, seemed to be made of stainless, rather
than tin-lead, and didn't solder well. That's why the hook pulled out in the
first place, bad solder joint due to a poor choice of metals for the hook
eye. If the motherboard uses plastic push-pins to hold the chipset heatsink,
those work pretty well. Those are actually hard to take off, for inspection
work, and there is a bit of danger, while compressing the end of the
push-pin, underneath the motherboard, that you'll scratch the printed
circuit board.
An ideal solution, would be if they used screws to hold the heatsinks on,
but they hate that stuff at the factory. It's always the "fancy" solutions
they want, like a retention scheme that can be installed by a machine.
And screws are something you might install with humans in the line. And
if you make 5 million motherboards per month, that would be a significant
expense.
Paul
