Unstable P4P800 Deluxe

When I bought this board 3 years ago, it was stable with PAT enabled (perf in auto, and MAM enabled). Now it fails prime95 and mprime within 8 hours. I have tried it stock, relaxed all timings, swapped in a new ps and a new CPU. I have pulled everything except the vid card and the OCZ memory. I have pulled alternating memory sticks, and everything fails prime 95. The memory passes memtest86.

What the heck... Is my mobo bad? Under load, my temps never get above 55c proc / 43c mobo for an 8 hour FAILED test.

Voltages are set to 1.625vcore, 2.85v vdimm, and 1.6v AGP/pci.

ASUS probe reports vcore dancing from 1.504 - 1.536v under test conditions. 12v is 11.855v - 12.100v.

see sig for normal config.

can you try a different CPU in the rig?

Can you yank everything but a single HDD, vid card and memory, take it all to absolute stock (NO OC AT ALL!!) and then try it?

It appears as though You have a vcore undervolting problem, especially as
You say Your vcore setting is 1.625v and Asus probe is reading 1.504-1.536v.
I performed the droop mod on my p4p800dlx, but where I had 1.525v set in bios,
Asus probe would read between 1.63 and 1.53 when under load, So the droop
mod on my mb served to keep the vcore up higher, to aid in overclocking. If You
are handy with a very fine soldering iron I would suggest trying it.
It could also be possible The capacitors on your mobo are not very good any
more, resulting in unstable voltage rails, generally if they have bulges on the
top You are in big trouble. I am not aware off the top of my head whether
or not the 3.4ee is a Northwood or Prescott core cpu. A mate of mine had a
3.2 prescott in a p4c800 deluxe and it also was undervolting, so after I told
him to up the voltage in the bios He had no more problems, his problem was
not as severe as yours though.

I don't feel comfortable putting a soldering iron to my motherboard.

If the voltages are drooping, then there must be something wrong with the board or the capacitors or whatever.

I will have to buy another mobo on ebay or something I guess. Can anyone suggest another socket 478 board based on a 865 or 875 chipset??

If I buy a p4c800 (875) mobo, I will probably have the same vcore undervolting problem, right?

I didn't feel all that comfortable when I did the droop mod to my mb, scared
the crap out of me at the time, everything so much smaller than it looked
in the pics floating around the net. I'm an electronics tech so of course
experience with that sort of thing helps.
I googled 3.4ee and found that it is a northwood cpu, amazing Intel got
the 0.13u chips to clock up that far on air. My 2.6c would only do 3.13ghz
100% reliable. I suggest that before going to the extent of buying another
mb You try upping the vcore to around 1.675v in bios and see how that goes.
this should bring the asus probe voltages up to 1.554 and 1.586 which might
stop it crashing under load. As long as You don't go to 1.7v You should avoid
S.N.D.S , sudden northwood death syndrome.
It is well known that most Asus Socket 478 boards overvolt the cpu, so Yours
is a bit strange, especially so as My exact same model of mb overvolts the cpu.

Best of Luck.

hi'
I had to set 1.50v for cpu in the bios to get it work stable!
now, after 4 hrs of orthos, never got over 47°c
so, I guess mine is undervolting a bit too ...

but my OC to 3.8 is rock stable.

i686