Too much undervolt results in no BIOS?

Hello!

A few months ago i bought a GA-MA78GM-S2H board and an amd 4850e to
fit in it. I also got all the other stuff to make a pretty decent
htpc, which has been running just fine ever since.

Last week i tried to underclock and then undervolt the cpu to see if i
could get the temperature down a bit. I'm at work now, so i don't
remember the exact figures, but i lowered the multiplier and vcore and
booted. Everything was fine, i got lower temps. I used it for a few
hours, then switched it off. A few hours later i came back, and it
wouldn't boot.

Opening the box, i saw that everything would power on (fans running,
disks spinning), except for the cpu fan and apparently the cpu itself
got no power either. I cleared cmos, and everything was back to
default and running just fine. I tried underclock and undervolt again
(same values), reboot, go into bios (worked fine, showing the new
values), then reboot after a few minutes. Again, dead cpu fan and
apparently no power to the cpu.

I don't know much about clocking either way, and certainly not much
about undervolting, but can anyone enlighten me on why it would not
boot? Especially why it boots right after the changes, but not the
second time?

"chhjposter" <> wrote in message
news:24901f4b-4611-47db-b706-...
> Hello!
>
> A few months ago i bought a GA-MA78GM-S2H board and an amd 4850e to
> fit in it. I also got all the other stuff to make a pretty decent
> htpc, which has been running just fine ever since.
>
> Last week i tried to underclock and then undervolt the cpu to see if i
> could get the temperature down a bit. I'm at work now, so i don't
> remember the exact figures, but i lowered the multiplier and vcore and
> booted. Everything was fine, i got lower temps. I used it for a few
> hours, then switched it off. A few hours later i came back, and it
> wouldn't boot.
>
> Opening the box, i saw that everything would power on (fans running,
> disks spinning), except for the cpu fan and apparently the cpu itself
> got no power either. I cleared cmos, and everything was back to
> default and running just fine. I tried underclock and undervolt again
> (same values), reboot, go into bios (worked fine, showing the new
> values), then reboot after a few minutes. Again, dead cpu fan and
> apparently no power to the cpu.
>
> I don't know much about clocking either way, and certainly not much
> about undervolting, but can anyone enlighten me on why it would not
> boot? Especially why it boots right after the changes, but not the
> second time?

I do some overclocking and at some point the system may boot once and fail
the second time. That is just one symptom that may pop up when there is
insufficient vcore voltages. The entire formula is the same with the
processor at default or lower than default speeds........the processor needs
a certain amount of voltage to run and a bit more to boot. A restart may
boot fine and a cold boot may not. A small vcore decrease probably is not
going to help the temps much just like a small increase does not raise the
temps a lot either.


Ed