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OC Help

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December 12, 2008 3:57:17 PM

let's get the preliminaries out of the way...

ASUS P5Q Pro
E8400
OCZ Platinum 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500)
ASUS EN9500GT TOP/DI/512M GeForce 9500 GT 512MB 128-bit GDDR3 PCI Express 2.0
ARCTIC COOLING Freezer 7 Pro 92mm CPU Cooler
Microsoft Windows Vista Home Premium SP1 32-bit

here's the deal...
did an easy oc to 3.6 (400x9.0) everything was fine and stable (both in normal usage and under prime95 stress).

but i'm pretty sure it could do more, so i took it to 3.8 (422x9). it seemed fine at first, but the system started to get a bit glitchy. i ran the stress on the cpu and it says all was fine. but the test that includes memory would bring up errors pretty quickly. that was true whether the memory voltage/speed was on 'auto' or when i had the speed manaully at 1066. anyway, i'm thinking that there is some tweaks i'm needing to do with my ram to make it stable. or am i missing something else?

i dialed back my settings to 3.7 (411x9) and everything is working fine, but i would love to take to the 3.8 or 4.0, but i need to run ultra-stable. suggestions?

More about : question

December 12, 2008 4:18:29 PM

During these changes, what exactly are you changing? If your only adjusting the FSB then the reason your memory isn't stable is because the divider isn't low enough and it's causing your memory to try to run above 1066 and its crashing.

There are so many things to consider when your OC'ing, I always focus on one at a time. If your looking for the best CPU OC, I always set my RAM to run at rated speeds regardless of the changes I make to the FSB. This way you know your isolating the CPU. Then once I have the CPU where I want it, you can play with the ram settings if you want, but your going to find your 1066 ram is fine at stock, and the performance increase you get by running it at 1100, if your even able, are so small its not worth the possible instability.

Also, when OC'ing your CPU, you gotta look not only at FSB, multiplier, and your memory speed/divider/voltage. But you also have to consider the voltage going to the Northbridge, the south bridge, the VTT voltage, the PLL voltage, etc.

If these settings are auto, and you try to OC too high and leave other settings lower that you think are safe, you might be sending a massive amount of voltage to one of these and thats bad news.
December 12, 2008 4:28:38 PM

right... but in theory with the memory i have running at 1066, shouldn't i have plenty of headroom for the cpu fsb?
i was looking to work with the voltages, but for whatever reason can't find them in the pq5 pro's bios.
December 12, 2008 4:40:57 PM

Most 1066 memory needs to be adjusted in the bios. It will default to 1.8v but really needs 2.1 or 2.2 to be stable at the rated settings. This might be an issue. I missed earlier that you said you already tried to manually set it.

I have OCZ Reaper 1066 and it was giving me weird timings, until I manually set it to 5 5 5 15 at 2.2V and now its perfect.

Increase your Northbridge Voltage, it might be called NB Core, it might be called MCH core. This will increase the power going to the northbridge which controls the communications bettwen the cpu and memory. I only had to increase mine .06v for it to be stable, but I've heard others having to change it as high as .3v.

I also had to increase my VTT by .1v

By tweaking these settings I was able to bring my core voltage down and decrease my temps.

At the end of the day your going to have to play until you find what works for your specific parts. The amount of people that have the P5Q Pro and an 8400 is insane, you should be able to google "Overclocking P5Q pro and e8400.
!