Cant get a good OC on my XFX 7800GTX Extreme

[+Torm+]

Hello,

I got two XFX 7800GTX running SLI that defaults to 490/1300.

I've read many posts where people have OCed these on stock cooling, and no volt mods as high as 600+ / 1400+.

Problem is, i cant seem to get mine stable over 503 / 1330 ! (one hertz more and i get artifacts on gametest 2 in 3Dmark05).

Both cards are currently cooled by Zalman Vf700 running at full blast and a 120mm case fan blowing outside air directly at them. Idle temps are 47ish. Max load temps after running rthdribl is as high as 80c!

If i hit the detect optimal freq button it usually detects NO increase (returns 490/1300) or a very small increase (497/1330).

Pushing the clocks manually, the self test fails at about 510 for GPU and at 1340 for mem. This is with driver version 81.89.

Now i DO get very good benchmark results (15035 in 3Dmark05) so im not complaining speed wise - but this being xtreme systems after all, i'd like to find out why my cards wont do more.

I have not tested them one by one as its a pain to switch off SLI on the DFI SLI-DR, so i dunno if i have one dud card or what.

Could it be the PSU? I got a Tagan 580W PSU rated at 38A on the 12v, so it should be ample. I tried it in both combined mode and dual rail mode, with no diff on results.

Anybody got an idea on what i could do to increase the OC? New BIOS maybe?

[perkam]

You need to reseat the vf700. That would explain the issue being with the core and non with the mem.

Perkam

[andL64]

you need better cooling (temps) and more volt so a vmod will help but only do it if you know....

[zakelwe]

If the artifacts are green squares then that is definitely temp related.

Regards

Andy

[Flak Monkey]

You need to reseat the vf700. That would explain the issue being with the core and non with the mem.

Perkam

Yep, do that.

[+Torm+]

Took of the Zalman today and found that it was seated properly. The AS5 imprint on the cooler and the GPU core were "perfect".

Anyhow i cleaned both off with Arctic clean reaplied AS5 and seated it again. Visual inspection indicates nothing but that they are seated properly.

Idle temp immediatly after boot, 40C. Started rthdribl.exe and after approx 5 mins core GPU temp was 82C! (other core was "cold" as rthdribl dont use SLI).
Ambient room temp at this time was 25C and case temp approx 35C (i dont actually have a case temp sensor - but my HD's both report 36C).

Very puzzling!

The artifacts i get in gametest 2 is single pixel "noise" all over the picture, mostly white dots it seems.
At higher ram speeds i get clasic "flashing triangles".

Obvioulsy a vmod would help me..unless the cards burn up!
Reason i made this post is that i do see others gettng great OCs on these cards even without any mods.

I did another test yesterday - and i took down my CPU OC and let it run at 2500 Mhz at 1,375V. I noticed that then i could OC my mem to 1,37Ghz! I'm starting to suspect that 2 OCed GTXs and one OCed FX57 just draws too much on the 12V lines too feed it all properly.

[Impaqt]

Have you measured your 12v rail to make sure its in spec?