OC interfering with GPU?

[Anymeans]

I have been experimenting with OCing an E6600 from 2.4G to 3.0+G using from 9x333 to 8x400. Std items C1E, EIST off..PCIE set to 100, and RGB set to fast, memory ratio at 2, volatge at 1.25 to 1.34 depending on the level of OC. 2G CL5 DDR2 RAM and GA965P DS3 (rev 3.3 mobo) and ASUS 8800 GTS 640MB video card and running Vista.

All that works fine... stable and definite CPU improvement in 3DMark06 scores.

The problem is that frequently (not always) when I run a check on 3DMark 06 my GPU scores almost half while the CPU is fine. For example on the very first test (can;t recall its name) in the very opening sequence when I have the computer at stock it gives me 60-65 FPS... when OCing it can drop to 20 odd! Can anyone advise what could cause this.

 

[darkstar782]

Sounds like your PSU is at its limit maybe.

When you overclock the CPU needs more power, the GPU is power starved and declocks.

 

[Anymeans]

Thanks for your reply.

OK... have a 550W PSU... you reckon too small... how could I test this??

Thanks

 

[rammedstein]

a 550W PSU if of good quality will be sufficient, that is, if it is of good quality, if it isn't i highly doubt it would do.

 

[Anymeans]

Sorry... should have given more detail: PSU=Antec Trio 550W.

I presume its reasonable quality.

If this isn't the issue what else could it be??

 

[krazynutz]

Dude, I have your answer. My compy was doing the EXACT same thing. And I have a cheapo 500W PSU running an OC of 3Ghz on with a 6400 and a 7900GS. Would go higher but need my SI-128 to show up tomorrow.

Anyway, up your FSB and MCH voltages by +0.1v. That should clear everything up. Did for me. Don't bother with the PCI-e voltage. Try it out and see if it works!

 

[Anymeans]

First try seems to be running fine... will play with it over the next few days to see whether consistent and I want to try to keep my Vcore down so will see whether can optimise.

The MCH +0.1. Any long term issues I should be aware of... not even sure what it does or where to llok for tracking purposes... is it one of the Speedfan readings?

Thanks

 

[krazynutz]

Both Wusy's OC guide and Tom's OC How-To say to up the voltages on the mobo so don't sweat it. +.01v is nothing, really. Glad it worked. Should stay stable for ya. Happy OC-ing!

Here's the How-To. It uses the same mobo so you'll feel right at home.

 

[Anymeans]

Thanks for all your advice so far. With your input plus from another board I have established what the problem was (although all a black box to me).

I wasn't aware that on CPUz you could see the PCIE link ratio (not that I understand what it is ). Anyway it turns out when I have the fps problem the ratio goes from 16x to 1x.

So I checked three things... CPU volts, MCH volts and PCIE freq. all against a 9x333 OC.

Results:
Stock volts and 100 PCIE link = 1x link
+0.1V MCH = 16x link
102 PCIE freq = 16x link
CPU volts 1.3 (up 0.05) = 1x link

So great... now have a specific test for probelm but 2 solns. Any advice on which is best (for long term stability/lowest 'wear' etc?).

Cheers

 

[krazynutz]

if everything was working fine before with the suggestion I had previously, leave it at that and don't sweat it. Other threads say to up the voltages even more but you only have to up them to cover what you're doing.

At 333Mhz FSB, you should be fine with 1.325V CPU and if the GPU is having issues, just up the FSB and MCH voltages +.1 each. Or, do one, then the other and see which one solves your GPU issue.

Good luck!

 

[Anymeans]

Sry Nutz... I'm not being very clear am I.

I can keep Vcore at stock ..1.25 and with either upping Mch by 0.1 OR increasing PCIE to 102 get the ratio from 1x to 16x.

Happy to do either just wondered whether any reasons for one over the other?

Cheers

 

[krazynutz]

OH! ha ha...well then. My mistake.

I know of people upping both the FSB and MCH voltages to +.3v and others upping the PCIE to 110. Your increases are so insignificant that I wouldn't even worry why they work. Just enjoy the extra oomph!

Cheers!

 

[Anymeans]

OK thanks mate

 

[krazynutz]

lol...I tried the 102 on the PCIE and it worked. I lowered my own FSB/MCH voltages!

Thank YOU mate!

 

[Anymeans]

Can I describe myself as an 'old hand' now??

 

[krazynutz]

ha ha....only problem is, when I OC'ed to 3.2Ghz, I had to up the mobo voltages again. Ah well...thanks though! Cheers!