Overclocking Possibilities...

well from the nvidia forum, the one guy mentioned that the 650i is not stable over 3.0. I have a 750i chipset (which to my knowledge uses the same chip re badged, gg nvidia) and there was a BIOs flash that helped to make stable overclocks so would look into that. i have the same memory as you and tired tinkering as well and found that stock was the best for timings and 1.9v works well. I was having some BSODs when i was first messing with my voltages and found that the q6600 does not consume much to get the job done. I am running mine at 3.2Gh at around 1.38-1.4v and lot of people are running 3.6 on air running in the mid 1.4v area. So you may want to mess with that. Maybe pick a goal speed and try playing with the voltage and running Prime. If you have the option to change your FSB multiplier, try changing it form 9 to 8, I know a lot of guys have been having stable over clocks with that.
So recap,
1.) check to see if you have the most current bios.
2.) Baby step your OC, document what you change, what works etc.
That is my 2 bits, hope it might have helped... i know what you are going through and it is frustrating as hell.

I went to the MSI mainboard BIOS download site and looked at the latest versions available for the 650i and 750i. I have the latest AMI V1.7 that was released 07/29/08. AMI V1.3 for the 750i was released on 11/19/08. With my limited experience I assume it would not be wise to flash with V1.3.

The Cosair TWIN2X2048-6400C4 has the SPD programed at: JEDEC standard 5-5-5-18 @ 1.9V and EPP standard 4-4-4-12 @ 2.1V. I have been using the EPP timings, but have since switched back to using the JEDEC timings until I get my computer stable. After I do my overclocking, and I'm sure my computer is stable, I will try the EPP timings again and see what happens.

Here is a comparison of 650i mb's at Tom's Hardware:

http://www.tomshardware.com/reviews/...ared,1609.html

The guy you mentioned from the Nvidia forum_aleiro_was referring to the limitations of his Asus P5N-E SLI and only being able to reach a stable oc of 2.7GHz with his Q6600. Tom's mentions the P5N-E only has a three-phase voltage regulator, whereas my P6N has a four-phase voltage regulator, so I'm not sure how important the voltage regulator is as concerning overclocking. Tom's, in their Performance Summary, does mention that..."The MSI P6N SLI Platinum is the clear overclocking leader..."

The major reviews I have read about the P6N all used Dual Core Intel processors for testing, so they are not much of an indication as to how Quad Cores should perform. I guess I need to go back in the forums when the Q6600_GO was released and see if I can find someone who was using a P6N.

Anyway, I should be able to do something with my Q6600 until I upgrade. When I upgrade to Windows 7 I should be able to find a good deal on a 780i and memory.

As far as I know my mutiplier is locked at 9_