IMO if you want to go for decent OC with a Q6600 G0 try P35 or P45.
I was able to take my Q6600 G0 to 3.6GHz 1.46v or 3.8GHz if I used 1.55v on P35. Things like CPU VTT are extremely important when you pass a 411 or so FSB. NB voltage eventually becomes important too. If your ram has an extremely tight tRFC setting like 21 it could inhibit your OC too. While search for max stay on a 1:1 ratio 5-5-5-15 tRFC 54-56. Tighten later after you've found your max. Also make sure you manually set your ram voltage. A lot of boards under volt performance ram. If your ram needs 2.0v and is getting 1.8v that could be problematic. Below is an old post explaining how I got 3.8GHz on air using a cheap ass IP35-E mobo-
Here's exactly how I am doing 3.8GHz with a Q6600 G-0 + the IP35-E and because it works for me does not mean it would for you. Hardware OC = luck of the draw.
Stay on a 1:1 CPU|ram ratio to squeeze those last MHz out so, 400FSB should = DDR2 800. I am @ 423x9.
Start relaxed, 5-5-5-15. You can tighten later when you are sure you are stable. tRFC should be between 42-56 and no lower for the best stability. Make sure your ram is getting the proper voltage. If it supposed to have 2.0v set that, do not leave it on auto. Stay on 2T. If you want 4Gb ram go with 2 stick vs 4x 1Gb.
Vcore- 1.54v ( You best have damn good cooling, and you may want to go water. IMO 1.46v should get you 3.6GHz with a Q6600 G-0) For a Wolfdale stay between 1.36-1.40v max IMO.
*CPU VTT- 1.2375 *This is critical for quad OC
MCH- 1.33v(if you are only going 400x9 leave this @ stock voltage)
CPU GTLREF 67%
PCI-e 100 for best stability
C1E and EIST are optional. Leave them on if they don't cause problems because they will help keep your rig cool.
Direct a small fan at your PWM heatsink area or mount a fan on it, if you care to bother.
I am using the Thermalright Ultra Extreme with Arctic silver 5 and quality 120mm fans. One is pushing air into the HS and the other pulling it out. I also lapped my HS base and the CPU for an added edge.
I have two 120mm Sharkoon Golfball Fans in push pull on my Thermalright ultra extreme. The fan facing the front of my case pushes air into the heatsink and the fan on the rear pulls air out. You may need to place something akin to silicon noise dampeners on the rear fan to stop it from brushing the HS.
These are the fans I'm using-
I secured them with zipties and control them with a Sunbeam rheobus-
A brief detail on lapping-
You may google "lapping your CPU" if you don't find the above links useful enough.
Also connect your components to good clean
power, or that is a quality PSU. That has helped me more with overclocking than you might think.
If you're using Vista get SP1 RC, and read this-