It took two nights to test most combinations with memtest. It seems that in my case (P4P800 DELUXE + Northwood 1.8A), the highest stable limit is around 2.8. It could reach 3.02 but apprently not stable under my system.
Right now, I run on FSB 156 to 2.84. Memtest showed no error beyond 1700%. Current setting is as follows;
Dual Channel (Physically DDR400 512 X 2 PDP system pc3200)
DDR 266 (Manual)
Performance : Turbo
V-core : 1.6
Ram Timing : 2-2-2-5-8
Memory Accelleration Mode : Enabled
FSB:RAM = 1:1
Through my tests, I found that DDR voltage and AGP volatge doesn't make difference. But v-core really affects stability.
I might get higher than current setting once I raise v-core more (upto 1.8). But I'm not sure whether 1.8 might burn CPU. Any comment on it?
Last thing which I haven't had a chance to test is PSU. I use my old P3 PSU (200w) with P4 adapter cable(12v) which might have affected stability my OC test. Does it make difference?
Concerning CPU temperature, I actually didn't take that much care since it didn't go up that high, even with FSB 168 (under 38).
I also tested both single channel and dual channel but found no difference in terms of getting maximum satable edge.