Overclocking

As we mentioned in the introduction, and as we've seen in our performance tests, something to note with the 7900 GS is that it seems to be fairly good at overclocking. This is a factor that could potentially make the 7900 GS a formidable competitor to other cards in its price-range. Most of our 7900 GS's in this roundup have factory overclocks, but many users are interested in doing their own overclocking, so with this in mind, we've done some overclocking on these cards ourselves.

To get our overclocks, we use a method of gradually bumping up the clock speeds using coolbits, and then stress-testing the cards (using game benchmarks) to ensure stable operation at the highest possible clock speeds. "Stable Operation" is basically when a game benchmark runs without any tearing or graphical artifacts due to heat, and also without any lowered performance.

Every graphics card overclocks differently, and it's important to take some precautions when doing your own overclocking to avoid damaging your card. The speeds we achieved here do not necessarily reflect the exact overclock another XFX or EVGA 7900 GS owner might be able to achieve.

GeForce 7900 GS Overclocking
Manufacturer and Card Factory Clock User Overclock
Albatron GeForce 7900 GS 450/660 524/800
XFX GeForce 7900 GS RoHS Extreme 480/700 597/824
EVGA e-GeForce 7900 GS KO 500/690 591/812
Leadtek Winfast PX7900 GS TDH Extreme 520/700 556/790
BFG GeForce 7900 GS OC 540/660 571/751

The XFX 7900 GS was one of our cards that overclocked especially well, along with the EVGA 7900 GS KO. Two of our 7900 GS cards that came with fairly modest factory overclocks managed to achieve higher user overclocks than the others. Unfortunately, the card with the lowest factory clock, the Albatron 7900 GS, also got the lowest user overclock, which is something of a drawback for this particular card. Below are the performance results at these clock speeds.



The data here shows the kind of improved performance these cards are capable of with further overclocking beyond the factory clocks. As expected, performance was the highest with the overclocked XFX and EVGA 7900 GS cards, and the improvements in framerates are impressive. In Oblivion for example, between the reference clocked Albatron 7900 GS and our user overclocked EVGA 7900 GS (591/812) at 1024x768, there is a 38% increase in performance. This kind of performance increase can mean the difference between being able to play at a higher resolution or with the quality settings turned up a little higher.

Even though the Albatron 7900 GS wasn't able to get as high of an overclock as the others, as the data shows, it still performs higher than most of the stock factory overclocked cards. Still, because there seems to be such variation between theses cards' overclocking ability, choosing the XFX or EVGA 7900 GS over the Albatron might be the best option if you plan to do your own overclocking. As we only have one sample of each card, we can't say for sure whether or not customers will be able match our overclocks or even exceed them, and as the saying goes your mileage may vary.

The Elder Scrolls IV: Oblivion Power and Heat
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  • Bonesdad - Tuesday, September 19, 2006 - link

    I'd have to go with the Leadtek card. Near to the BFG in almost every level of performance, nearly equal in watt consumption, lower heat output under load, a couple of (suspect, I admit) games included. the (maybe) $20 more is worth it for the heat output alone to me.

    Also, why no noise output comparisons?
  • Nimbo - Tuesday, September 19, 2006 - link

    Why ATI cards are not overclock in the reviews? Are they bad overclokers? Why are not factory overclock versions?
  • DerekWilson - Tuesday, September 19, 2006 - link

    ATI's current generation of GPUs have not been good overclockers. It is also not as easy to find ATI factory overclocked cards.

    We will look at ATI overclocking in similar roundups of ATI cards.
  • formulav8 - Tuesday, September 19, 2006 - link

    I was hoping to see a 7600GT including in the mix to see what I would have to gain from a 7900gs. :(



    Jason
  • Josh Venning - Tuesday, September 19, 2006 - link

    The 7900 GS launch article compared the 7900 GT to the stock 7900 GS, which you can take a look at here: http://anandtech.com/video/showdoc.aspx?i=2827">http://anandtech.com/video/showdoc.aspx?i=2827. We tested these overclocked 7900 GSs on the same system, so you can compare the numbers directly (with the exception of Oblivion which we tested with different quality settings for this article).
  • yyrkoon - Wednesday, September 20, 2006 - link

    Hmm, only roughly 5FPS more on the 7900GS vs the 7600GT acrossed the board. Thats pretty sad, but I think I know what I'll be doing when I get a conroe system going, I'll be adding another 7600GT for SLI . . .
  • DerekWilson - Wednesday, September 20, 2006 - link

    across the board is a little off I think ... in bw2 and oblivion, yes the fps difference is low. But when 4.2 fps is the increase over 17 (a 24% difference), you can't ignore it -- it does make a big difference. I would tend to argue that at these very low framerates, a 5 fps difference is much more noticable than the difference between 60 and 120 fps. In most other tests (especially with AA) frame rate differences were much higher in addition to being higher precent differences.
  • DerekWilson - Tuesday, September 19, 2006 - link

    http://anandtech.com/video/showdoc.aspx?i=2827">http://anandtech.com/video/showdoc.aspx?i=2827
  • sum1 - Tuesday, September 19, 2006 - link

    "The BFG 7900 GS OC's core clock is set at 520MHz, a 70MHz increase over the standard NVIDIA 7900 GS"
    It’s listed at 540MHz everywhere else.

    "EVGA"
    Is usually written eVGA.

    "Something slightly unique about this 7900 GS..."
    Uniqueness does not come in shades of grey.
  • rushfan2006 - Tuesday, September 19, 2006 - link

    You are WRONG on all 3 of your points....Stop being so damn anal for the sake of just busting stones because you are bored.

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