Was trying just how far I can UNDERvolt (there can't be any harm in
that, now can there???) the sucker and still have a stable system so had
it running prime95 for the night.

When I woke up, the screen wouldn't
come out of standby anymore for lack of any signal. After some messing
around, I figured Asus' weird speech POST (now I know at least ONE
reason why it perhaps could be of some use, before I thought it was a rather useless piece of marketing fluff) says system failure, cpu
error. BIOS reset and the like didn't help, removing and reinstalling
the CPU didn't either. So I guess the sucker somehow fried (before it
was running under full load at 54°C for 3 hours with me working on it,
rock solid...).

That's strange! Undervolting shouldn't cause that. I've gone too low plenty of times with my Newcastle and everything's been fine.

Anyone got any ideas?

Maybe the CPU's been bad all along and just now fried? I really hope that was the case, as the rest of the compontens behave fine (I'd hate to know it was the Etasis but that should shut down in case of overheating)...

I've had at least 15 AMD CPUs in the past 5 years and none of them ever failed (except the odd one I clearly destroyed , so I'm not turning to Intel just now

I've never heard of such a thing either. I've used (and currently use an A64m) dozens of AMD CPUs over the years, and have had trouble trying to fry them - Namely a Slot A Athlon 500 with just passive cooling.

I personally think that:

1. It may be a problem with the motherboard - I've heard of some models going to sleep and never truly waking up.

2. You do have a bad chip that through some sort of voltage starvation died on you (as strange as that sounds).

I'd RMA both, if possible - Do the RAM too. Might as well as do it all just to make sure.

Perhaps this is a stupid question, but did you try clearing the CMOS? I'd at least try moving the vcore back up before you assume the cpu is dead.

Yeah I would just do my standard component test if I were you, which is mainly based on ease of application:

1. First try some different RAM, if you have any compatible stuff. If you don't then maybe you could borrow some from a friend.

2. If RAM tests yield no results, then that's not causing the problem. So I would test CPU/MOBO next. Borrow from a friend another compatible CPU and do a switch: put your CPU in their MOBO, put their CPU in your MOBO, and you'd be able to figure out exactly what the problem is right away.

Obviously this test depends on your friends or acquantences having compatible parts. If you don't have a way to attain some test parts, then I would go with what POLIST8 said and just RMA the CPU, MOBO, and RAM. Out of curiousity, what CPU and MOBO are you using exactly? I may want to avoid them in my future purchases

I assume that's what he meant by:

you could also take out the battery for a while (night or so) and see if it boots the next morning... like POLIST8 said: undervolting should not fry chips in general. Do you have any other machines to try the cpu on? Maybe some friend's machine?

No luck it seems. If only I could truly tell if it's the CPU or the board...

It's probably easier to RMA the motherboard than it is to RMA the CPU (and if you have a retail CPU, it'll have a much longer manufacturer's warranty), so I'd do the motherboard first.

This is my "out-on-a-limb" advice, but try removing the plug from the PSU, turning it on and completely draining it.

When I undervolt my CPU (an Athlon XP mobile, albeit), I sometimes have what seems to be a dead CPU. I see the fans spin up, but no POST. I swapped PSUs and it appeared to fix it. But when I plugged my Seasonic SS-300 back in, it fired up with no problem.