E6600 no more than 3.1Ghz max.

what kind of voltage you runnin?

Thanks for the reply techgeek, I read that tutorial briefly but it did not specificly highlight my problem anywhere. My voltage set is 1.325.

Another thing, whenever the CPU is idle, it seems (or so it shows in CPU-Z) to downclock, is this a good thing to happen, does this happen by default? Because I certainly didn't set anything to do that in the BIOS. The BIOS is also at the latest version.

Thanks very much,
Orbixx.

Corsair Dominator XMS2 2GB PC26400 DDRII800 CAS 4-4-4-12. Motherboard automatically adjusts the memory as I changed the clock speed in the BIOS.

try something like coretemp or intel's TAT to measure the temperatures of both cores. if your resluts are the same, something is wrong with your contact between cpu and heatsink. one of your four push pins may not be properly seated, you may have a concave IHS, or many other things. Let us know once you get some temp readings from another app.

EIST=SpeedStep, this should be disabled during OC'ing. There is something called Vdroop which is in essence is a slight drop in Vcore during high CPU usage. Every motherboard has this to some extent and is actually mandated by Intel's VRM design guide. Now in a non-OC'ed system Vdroop doesn't cause a problem, but it can and does cause problems for OC'ers. The reason being is you may adjust the voltage so your system is stable when CPU is idle, but when the CPU usage jumps resulting in Vcore to droop (because of the raised clock speed, the swing between Vcore(idle) and Vcore(loaded) is greater), it can cause your system to BSOD, reboot, insert some nasty behavior here. So you continue to add voltage until it's stable under load. This is great while under load, but in some cases switching from loaded to idle suddenly can cause the same symptoms mentioned above when Vcore shoots back up. Of course OC'ers find a happy medium here and find where Vdroop doesn't affect system stability (or they mod their motherboards to reduce or eliminate Vdroop). Here is where EIST comes in, if EIST is enabled and lowers the multiplier (only happens when system is idle), the result is an even bigger swing from Vcore(loaded) to Vcore(idle). As you can imagine this increase voltage swing can cause your system to be unstable.

So in short EIST and any thermal management should be disabled to achieve a maximum stable overclock. This is one of the steps in Wusy's guide, although the reasons aren't explained.

Also with your voltages, these are important when overclocking. You will only go so far with stock voltages as you have discovered. If you are determined to get higher you are going to have to raise Vcore, MCH, FSB termination, and likely the southbridge voltage as well (read the guide carefully, all is explained although it's general as it refers to more than one motherboard). Also you have to make sure the PCI and PCI-E bus are locked at 33MHZ and 100MHZ respectively (also explained in the guide). Overclocking these will definitely affect system stability and could cause HDD corruption (for PCI) or graphics card instability or damage (for PCI-E). Overclocking these buses never really results in any performance gains anyway, but has a huge affect on stability. Some people have experimented with overclocking the PCI-E bus, and found little to no gain, but I have heard of damaged graphics cards by doing so.

Lastly I would not attempt any further overclocking (in fact if I were you I would go back to stock) until you get a good aftermarket cooler. Those temps are too high to continue.

Yeah, I went back to stock last night. I'll buy a nice cooler relatively soon. So anything over 3.1GHz even with an aftermarket cooler you wouldn't recommend?

And I haven't touched my ratio, not sure what to do with it to be quite honest.

Also I read that my Northbridge ought to be cooled quite dramatically, is there a specific type of fan that will do this? I've never had to cool the Northbridge.

Heh, I really need to read into this. I'm thinking of going watercooling, but is it possible to watercool a 8800GTX that already has a HSF on it?

I'll also look into the ratios, thanks!

No you should have plenty of room to overclock beyond 3GHz, just not with a stock Intel cooler. I would guess that you could hit 3.4 - 3.6 easily if you can keep your C2D cool. You managed to get a 25% overclock stable without touching Vcore, so you have plenty to play with.

Like I said if air cooling is enough for you, check out www.anandtech.com and pick any of their recent cooler reviews. The charts near the end of the review will have all the coolers they have reviewed. This will give you a good idea which perform the best (hint: ThermalRight Ultra 120 Extreme) and you can find one that performs well and fits your budget.

Let us know how you make out. Good luck.

Yep, I've decided if I'm gonna bother cooling my system further, I might as well go water cooling. What would be the best thing for my system combination? I'd want a 8800GTX block and a northbridge block too, I guess I'd usually have to buy them as extras right?

Set your memory ratio to the lowest setting. Think about this: If you get your CPU to 400MHz FSB, the lowest memory setting (1:1, gigabyte calls it 2.0) will also be 400MHz clock rate, which is 800MHz data rate, which is what your memory is rated for.