Asus P5B (vanilla) Overview

[Timbosan]

Nope, stock cooling and the 120mm I have over the RAM cools it plenty. Board is full vmod but I only used 1.55 vmch for 550 which is why Im thinking it still has plenty of headroom.

What was its max FSB with stock vMCH? do you run vMCH 1.55v 24/7? What are NB temps like?

I had to find out if it was cpu or mobo:
I have just completed the vMCH (northbridge) voltage mod for my P5B using a 50K 25-turn VR. Im using the stock NB heatsink with AS5 and a 40mm fan @ 5v.
Intel states 1.375v as an absolute maximum, i am running it at 1.36v. Stock voltage was 1.29v. When benching it is warm to the touch, probably ~30 - 40*C. Im not stable at any higher FSB than i was before. I must be CPU limited.
However, it has allowed me to run static read control on 'faster' (memset says performance level = 10) and remain 100% stable @ 490 FSB. Before the mod it wouldnt even boot with those settings.
This got me about 65 MB/s more bandwidth & 0.6 ns lower ram latency, so ive gained something.

I´m kinda hitting a wall at 520fsb, but i can´t be sure if it´s due to ram(i´m using 1:1 divider, running ddr2-800@1040, gskill pk)

Your ram may be at its limit, it uses promos chips