P4P800 DDR400/5:4 Unstable - DDR400/1:1 Stable | Why?

[Akumajou]

Why can this Asus P4P800 run DDR400 stable at 200FSB/1:1, but not at 250FSB/5:4 when the timings and voltage are the same? It actually requires the highest voltage of 2.85 to get into Windows before it crashes, while 1:1 runs fine at 2.5/2.65.

[ctal]

Are you sure it is the memory that is producing the instability? Perhaps the cpu or the northbridge or the mobo itself can't handle the 25% overclock. I don't think that the voltage sensitivity you mentioned necessarily means that the root cause of the problem is the memory.

That said, I do recall seeing some comments when the 875/865 boards were out indicating that at least some of them overclocked better with 1:1 memory ratios than with other ratios. I found no major differences in that respect, though, with my P4C800 Deluxe (an 875 Canterwood board), in which at various times I used both low latency memory at 5:4 and higher speed higher latency memory at 1:1. But I was cpu-limited to a 16% overclock (232 fsb), using a P4 2.8C.

In the bios, you might try setting Performance Mode to Standard, and Performance Acceleration Mode to Auto, if they are not already set that way (assuming the P4P800 offers those settings; I'm not sure the 865 chipset provided both settings as the 875 did). I think those are the settings most conducive to stability.

Regards,
-- Al

[Akumajou]

Another oddity of this is that it's much more stable (although I'm not sure if 100%) with 2.5, 3, 3, 6 memory timings at 250FSB/5:4 than 3, 3, 3, 8 or 3, 4, 4, 8...

[traveler]

I run my P4P800deluxe RAM at 2-2-2-5. Both the Mushkin and the OCZ took those timings 1:1 with a mild OC.