Overclocking my two Saphire AMD HD 7950 GPUs

[TX-ScubaSteve]

Just had an unusual experience (well at least for me) trying to OC my video cards.  Granted this is the first time I've ever really tried with any "success".  The last card I tried to OC, was my 8800GTX which would crash with just one 1Mhz of clock increase of the core.

Anyway, I tried testing for stability with FurMark (and MSI Kombustor--which is basically the same thing), and found I was able to max out both the core (1200Mhz) and memory (1575Mhz) frequencies with no artifacts or hangs, and temps on both cards didn't get much above 62C.

I then lowered the voltages as much as I could while still maintaining stability.  After that I tried 3DMark11 to benchmark--excited to see just how much higher my scores would be!  However, 3DMark11 would crash instantly upon loading the first scene.  I also found that Heaven Benchmark would also crash.  So much for FurMark!

I set memory back to default and reduced the core frequency till I got Heaven to run.  3DMark11 was more finicky and required even a lower frequency before it became stable.

After bumping up memory frequency, I found I could max that out with 3DMark11, but my scores were horrible!  Dropping from P14454 to P9300!  As it turns out, my stock memory frequency gives me the best performance by far!  I also tried lowering the memory frequency below stock (including matching with the core frequency) and found that also reduced 3DMark11 score, but not as badly as increasing the Memory Frequency by 25Mhz above stock!--and that with maximum memory voltage of 1.7V!  There's no difference in performance when I set Memory voltage to 1.7V or the stock 1.6V.  Performance is reduced though when I lower Core voltage and/or Core frequency from the maximum 1.3V and 3DMark11's max stable speed of 1125Mhz.

So right now, I have my Core set at 1.3V-1125Mhz, and Memory is at stock: 1.6V-1250Mhz.

My benchmarks on ROF were disappointing.

Before GPU overclock: Average: 57fps, Minimum: 46; Maximum: 84
After GPU overclock: Average: 62fps, Minimum: 46; Maximum: 84

My 3DMark score went from P14014 to P14454

From stock CPU and GPUs settings to OC CPU (4.5Ghz) and GPUs:

ROF: Average 52-62;  Minimum 39-46; Maximum 78-84
3DMark11: P13586-P14454; Graphics: 14766-15243; Physics: 12193-13911

[TX-Gunslinger]

Very interesting, Stephen.

My experience with this build (almost identical to yours except for your Graphics card) has been:

1) Benefits from OC of CPU + GPU + RAM :  Completely not worth the time, expense or trouble.

2) Benefits from having 6 cores :  Potentially huge, if I use the capability.  Why?  Yesterday I conducted a test while running ROF + newest version licensed Fraps capture + 1080p capture from USB camera positioned behind my cockpit (so that full screen video + 2nd Video of control actions could be recorded).  Result?   No frame loss in ROF.

Currently max'd out ROF uses approx 33% of my CPU.  There's a lot more headroom there for other, concurrent applications.

My current theme, is to "fly more" and "stop tweaking" so that I can use this thing for what I bought if for.  That means time spent in single player to improve my shooting - time spent in MP to improve my survival.

S! and thanks for sharing