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****The Official 7900 overclocking thread****

nO}{8 said:
yer overclocked to 600/1640, but i was expecting more.
Click to expand...

At those clocks, that's about right. You should be able to get a bit higher though if the volt mods are working. The only problem is that it's summer now and if you've got the same problem as me then ambients temps are up 10, I repeat 10 degrees where my computer sits.

I got 14k odd with the 1.4v mod on both cards (620/1660 i think, though there was probably more room), but my temps are going nova even with light gaming so i'm running them slower again and will probably remove the mod if I get any crashes or artifacts. So far so good though, i've managed several hours of Oblivion and UFO: Aftershock (the later being strangley the more punishing in terms of stability) without problem, though i'm idling 50C on the cards and 60C under load.

More surprisingly though in this heat is that my CPU is stable. When I first got it i couldn't get it past 2.65ghz. Slowly but surely though i've been pushing it up, loosening a timing here, upping the voltage there, and I'm at 2.81ghz now and holding. 42c ldle, 54c under load.
 
I've managed to get my 7900Gt to 585/1490 without the volt mod.
Couple of questions though. It seems I have a very low memory speed compared to everyone else who manage get 1600 with ease. I get glitchy graphics when i go above 745 (3dmark06 wont work etc). Is there a mod i need to do to the memory?
With respect to the core, am i at the limit as to what i can get without the volt mod? What sort of speeds should I obtain with the 1.4V mod? What voltage does the GTX run at at stock. I have a zalman 900 fitted.

Finally, If I got another 7900, how can I get both overclocked? Are they individually tweakable when both installed and in SLI? I take it SLI would run at the slowest cards speed.

Thanks

Gommsta
 
Gommsta said:
.....Couple of questions though. It seems I have a very low memory speed compared to everyone else who manage get 1600 with ease. I get glitchy graphics when i go above 745 (3dmark06 wont work etc). Is there a mod i need to do to the memory?
Click to expand...

This is the first and only card i've had that seems to have to balance the memory and core speeds for optimal performance (it also have a voltage limiter on it, which I suspect might somehow be the cause). Anyway I ran into a similar problem with my memory when I first overclocked. I hit a ceiling well under 800, but then my core was high, about 580 like yours. I found that by dropping the core by as little as 15-20 allowed me to put an extra 150+ on the memory, which lead to faster results overall. I'd try lowering the core to say, 560, then try push the memory up. I bet you can get 560/1700, perhaps even a touch higher.

As for the idea of volt modding the memory, it's best not to. It will give you an extra boost (10% ish), but it will likely burn the memory out too.

Finally if you do go SLi the cards will clock simultaniously. Just be careful and don't try to run them in SLi at high speeds if only 1 is volt modded.
 
Hi, thanks for your reply.

I've tried putting the core down in steps, all the way to 450 but the memory refuses to work above 745. As soon as i select 750 then it gives up and 3dmark wont run.

Maybe i just got a crap card.

Cheers anyhow.

Gommsta

P.S. For Sli i'll probably run 550/725 when i get my card. That should be ok i guess.
 
Running the 7900GT`s Sli at stock is plenty, but nice if you can clock them. Mine are volt modded to 1.4 volts, and have been rock solid since day one, well apart from when i pushed them too far that is. Find a happy medium and stick with it.
 
Just an update and a bit of a quirk i found with the 7900GT.

As noted previously, I couldn't get past 745 on the memory. As soon as I tried 750, then 749 etc it woudlnt play ball. I put it to 775 earlier and it worked fine!
Its now running solidly at 800. Bizarre?

In the range 746-755 it doesn't work, above and below is no problem.
Core at 585 Memory at 800 now.

Happy me :D

still only gave me another 100 3dmarks lol

Gommsta
 
Gommsta said:
Just an update and a bit of a quirk i found with the 7900GT.

As noted previously, I couldn't get past 745 on the memory. As soon as I tried 750, then 749 etc it woudlnt play ball. I put it to 775 earlier and it worked fine!
Its now running solidly at 800. Bizarre?

In the range 746-755 it doesn't work, above and below is no problem.
Core at 585 Memory at 800 now.

Happy me :D

still only gave me another 100 3dmarks lol

Gommsta
Click to expand...

How odd! :p
 
Gommsta said:
Just an update and a bit of a quirk i found with the 7900GT.

As noted previously, I couldn't get past 745 on the memory. As soon as I tried 750, then 749 etc it woudlnt play ball. I put it to 775 earlier and it worked fine!
Its now running solidly at 800. Bizarre?

In the range 746-755 it doesn't work, above and below is no problem.
Core at 585 Memory at 800 now.

Happy me :D

still only gave me another 100 3dmarks lol

Gommsta
Click to expand...

OMG is that true? Ive got exactly the same problem! coolbits detected 1568 for my mem but i chose to run it at 1500 and in certain apps the screen goes completely bonkers but it runs through 3dmark without any problems :confused:

I'm running at 1490 at the moment and its fine. Gonna try 1550 when i get home :D
 
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