Stuck while trying to OC a Q6600 on a Gigabyte MB - advice requested.

[Zithras]

This is my first time trying to do a major overclock, and the Gigabyte BIOS is driving me nuts. First, the basics:

CPU Q6600 G0 SLACR (lapped)
MB: Gigabyte GA-X48-DQ6 (unfortunately, it's so new that its hard to find info on)
cooler: Xigmatek HDT-S1283 (also lapped)
PSU: PC Power and Cooling S75Qb 750W
video: Zotac GeForce 8800GT 512 MB
ram: G.Skill 4 GB (2x2gb) DDR2 1066 (mfr. specified voltage is 2.1, with 5-5-5-15 timings, when the motherboard is set to autodetect timings, it gets 5-7-7-20, right now I have it dialed in to the recommended 5-5-5-15)
fans: 5x Thermaltake A2016 80mm variable case fan

I'd like to overclock the chip to 3.6 GHz (from 2.4) by raising the voltage to about 1.48 and the FSB to 400. When I do this, the computer posts and boots, but as soon as a start a Prime95 stress test, the computer restarts in a couple seconds.

I *think* the problem is in my RAM settings. Apparently the RAM settings on the Gigabyte bios are somehow tied into the FSB settings, but I don't understand how. (i.e. changing my FSB to 400 does strange things to my RAM, such as making it run at 1200 rather than 1066, etc)

My question is this:
What should I set my RAM System Memory Multiplier (SPD) to in the BIOS when I overclock the Q6600 to 3.6 (400 FSB)? What about with the processor at 3.4 (If 3.6 will not work with my components - although I REALLY hope it will)

The SPD menu (used to set RAM frequency) is set as follows (and only contains these choices):
Auto, 2.00A, 2.50A, 3.00A, 4.00A, 2.00D, 2.66D, 2.00B, 2.40B, 3.20B, 2.66C, 3.33C, 4.00C

The explanation for this menu reads as follows:
Auto -> Set memory frequency by DRAM SPD data
(G)MCH strapping: x.xxA -> FSB 266 MHz; x.xxB -> FSB 333 MHz; x.xxC -> FSB 200 MHz; x.xxD -> FSB 400 MHz

Should I run this RAM lower? Higher? Get different RAM? Will it help to underclock the RAM? How? I don't understand how to 'fix' the RAM problem when I OC the CPU.

Quick summary: What SPD memory setting should I use with 1066 RAM when overclocking a Q6600 to 3.6 GHz (400 FSB)? What about 3.4 GHz? (378 FSB I assume)

Thanks for the help! (and tell me if I need to post anything else)
Zithras

Also, if anyone has experience with this motherboard/general cooling setup, is 3.6 GHz stable a reasonable goal? Or is that only likely if I get a reallly lucky set of parts? Anything else I should try?

 

[scrappy66]

I ended up under clocking my ram I run fairly smooth. I have a problem every now and then when I boot up it will repost @ 2.4 and I set it back to 400. I run fine until it dose it again. I have no BSOD's no Freezes or lockups at all just the post issue. I have had mine for about a week still cramming away.

 

[Evilsizer]

use rated timings in bios by manually setting them... also it sounds like you need to increase cpu voltage to about 1.55. set your cpuvtt to 1.33-1.35 v with NB voltage at 1.37, sorry i forget the ranges that board has. maybe you could post up the ranges it offeres or pics of the bios if you have a cam.

BTW stick to using the 2x multi for the ram ratio.. yes fsb is tied to ram speed, so if your runing 400mhz fsb on 2x that would make the ram ddr2-800. that gives you till 533fsb to find out if the cpu can handle that high a fsb speed. as your ram is rated for 533/1066 speed.