Before I explain my problem lemme go over my system specs and such. I got a P5K-E motherboard, 8800gt gpu which is oc'd to 700 core, 5-5-5-15 timing ddr2 800 ram, windows xp w/sp3, 600W power supply, a tuniq tower 120 for my cpu cooling, and a Q6600 with G0 stepping.
My ambient room temperature here is around 68-75 F so its prety cool down where I am.
I use Coretemp and Speedfan to read my temps both of which seem to match and are accurate.
I use arctic 5 thermal paste.

Well I oc'd my FSB to 333MHz so my Q6600 is at about 3.0GHz now, I gave it 1.40Vcore, which from what I hear is a lot for that oc. I run prime 95 overnight and come back and end up seeing that one of the cores had an error, I dont understand why my oc's on this card are so unstable with such a high vcore.

I've listened to guides on this site and other site and disabled and enabled the right features on the MB to make the overclocking easier, but I always seem to have an unstable OC unless I throw my vcore up to like 1.5V which practically no one usued for just a 3.0GHz oc.

Its just that I see people pushing their Q6600s to 3.2 or 3.4 GHz with my vcore and saying thats its perfectly stable, but I cant get that with 3.0, I dont exactly know what I'm doing wrong. Are there any other ways to make your processor more stable that I might not know of?

Thanks a bunch

Wow that sucks, you should be able to do 3GHz @ stock Vcore.
How long does it take to error out?

What temperatures do your cores reach at 100% load?

What brand of PSU are you using?

What do you have Vdimm set at?

Have you tried running at 1.325V for Vcore? Will it even POST at that?

It seems that throwing more volts at it isn't getting you there, which means the problem isn't Vcore related. I don't know all the intimate settings of your motherboard, so if it's a BIOS set up issue, someone that actually has that board should be able to help.

Once thing you can do to isolate if it's the motherboard holding you back, is lower your multiplier to 7 and keep the FSB at 333. If it stays stable with Vcore @ 1.3V, then you know that your motherboard can handle the FSB. If it isn't then you need to look at tweaking your NB.

Its pretty stables if you ran prime95 for around 30min, i guess overnight one of the cores eventually errored out, so pretty long.
I've seen the cores climb to around 63 to 64 C at full load, but not much higher.
I'm using a rosewill PSU.
My vdimm is at auto for now, but it wasnt much more stable when it was at 1.9V with its max voltage being 2.0v.
Nah, I havent, is there anything special about that vcore that you can tell me?

Thanks for the tips, but how would I go about tweaking my NB, do I just change its voltage or is there some other way?

Well, if you didn't melt your system I'd say you did pretty good

Try updating to the latest bios.

Would get a better psu.

Whats wrong with a rosewill psu? I didnt know the psu was so closely related to the stability of a cpu.
And if I do get a better psu, what would it be, OCZ or Corsair?

PSU Quality is something that most builders overlook. Rosewill PSU's are NOT quality PSU's. It works, but still. Remember, overclocking is pushing the limits of your hardware, so it really depends on how good your hardware is that determines how far your OC will go.

PC Power and Cooling makes very very high quality PSU's

Well 64C isn't too high, but it's not great either. Not likely holding you back. I think once you get Vcore down to a reasonable level your temps will drop.

As for your choice of PSU, RoseWill isn't the most reputable brand. That's not to say changing out your PSU would buy you any reprive from your overclock wall.

As for RAM, what brand of RAM are you using? Specific model would help.

I didn't necessarily mean that there was anything special about that particular Vcore, but it's probably very close to your VID. If you try it and you find you are no less stable, you'll know that more Vcore isn't the answer to your problem.

Well voltage is one way that you can adjust the NB. Another is Strap, this will loosen internal timings in the NB as well as some RAM related timings.

Another thing I forgot to ask is are you using a 1:1 FSB:RAM ratio. If you are using a higher ratio, you could be inadvertantly overclocking your RAM.

To give you a frame of reference, I am running my Q6600 G0 at 3.2GHz (8X400) with only 1.325V for Vcore. Not all CPU's are the same however, but you shouldn't have to use 1.4V to get to 3.0GHz.

Changing psu would probably improve the stability of the power delivered to the cpu.

I agree with Shadowthor,

But then again, hopefully he doesnt buy some 120$ PSU and not get any better results

Sorry for late response, but if your still there it would be appreciated

This is the exact ram I have, I have 4gb of it, http://www.newegg.com/Product/Prod [...] 6820231098
Can you please explain more about the VID and how to change that, I'm not entriely sure, thanks
And yea, im using 1:1 ratio
also how effective would it be if i changed the NB voltage on my stability?

Thanks a bunch

VID is a Voltage Identification Digital that Intel puts on each CPU based on a test they run on each die. This voltage range Intel guarentees that a particular die will run at stock speeds. VID can not be changed. The VID can be different (and is) between CPU of the same speed bin. Typically the lower a VID a CPU has the less voltage required to overclock. If you want to know your CPU's VID, RealTemp shows it. The only reason I mentioned it was that I was giving worst case scenario, I think some of the highest VID for the Q6600 is 1.3250V. So I used that as my starting point for suggesting Vcore.

First try booting with a Vcore of 1.3250V. This may not be any more stable than what you have now, but if it isn't more unstable then that should lower your temps. Also if it's no more unstable, then we know it's not Vcore holding you back. I suspect that Vcore isn't your problem.

I was looking at you motherboard and it's based on the P35 which handles a FSB of 1333 without a problem, in fact it's the lowest officially supported FSB as I understand it. Just to go over the basics:

Ai Overclocking [Manual] of course which exposes the settings below
CPU Ratio [AUTO]
FSB Frequency [333]
PCIE Frequency [100]
Dram Frequency [DDR2-667]
DRAM Timing Control [Manual]
CAS# Latency [5]
RAS# to CAS# Delay [5]
RAS# Precharge [5]
RAS# Activate to Precharge [15]
TWR [AUTO]
TRFC [AUTO]
TWTR [AUTO]
TRRD [AUTO]
TRTP [AUTO]
DRAM Static Read Control [AUTO]
Transaction Booster [DISABLED]
Clock Over-Charging Mode [AUTO]
CPU and PCIE Spread Spectrum [DISABLED] disable both
CPU Voltage [1.3250V] start here, it should be more than enough for this modest overclock
CPU Voltage Reference [AUTO]
CPU Voltage Damper [ENABLE] this helps reduce Vdroop much like LLC
DRAM Voltage [2.0V] this is the upper limit of your RAM, you can try 1.9V if you like
FSB Termination Voltage [AUTO]
North Bridge Voltage [AUTO] for now anyways
North Bridge Voltage Reference [AUTO]
South Bridge Voltage [AUTO]

CPU Configuration
CPU Ratio Control [AUTO]
C1E Support [DISABLED]
Max CPUID Value Limit [DISABLED]
VanderPool Technology [DISABLED]
CPU TM Function [DISABLED]
Execute Disable Bit [your choice] I usually disable
PECI [DISABLE]
Intel SpeedStep Tech [DISABLE]

These are basics and I hope it gets you stable and a starting point. Also one other thing, have you tried running Memtest? This will eliminate your RAM as being the problem.

Please if anyone else has some suggestions or sees something wrong with the setting I have suggested, feel free to jump in.