Overclocking

As with the 7800 GTX, how the 7800 GT overclocks (beyond the factory clock) is something that we'll be looking at closely. Many of the 7800 GTXs had impressive factory overclocks, and the GT series looks to be no different. As we mentioned before, the XFX GeForce 7800 GT comes out of the box with a factory overclock of 450MHz core and 1.2GHz memory clocks. We were curious to know if we would be seeing the same core clock scaling that we saw with the GTX; specifically, if the performance increases were between the same frequencies.

Just to review, here is a brief explanation of what we saw happening with the 7800 GTX when adjusting clock speeds. Basically, we were seeing plateaus where consecutive core clock speeds had barely any impact on framerates (only a few tenths of a frame per second), then intermittent jumps up in performance between frequencies (i.e. between 472MHz and 473MHz). And because you get increasingly longer "plateaus" of minimal increase as you raise clock speeds, we've shown that this can cause for some confusion about how much faster each of the vendors' factory- overclocked 7800's really are.

After running some tests with Splinter Cell: Chaos Theory, we found that the frequencies didn't match up with what we saw with the 7800 GTX. We didn't see any jump in framerate between 472MHz/473MHz as we did with the GTX; instead, jumps occurred between 461MHz/462MHz and 477MHz/478MHz. We will be looking into this more closely in the next 7800 GT article, and hopefully, we can shed some more light on NVIDIA's frequency selection issues.

Interestingly, while attempting to overclock this card (the XFX GeForce 7800 GT), we managed to reach a core clock speed of 477MHz, which is actually a higher core speed than both the reference 7800 GTX (430MHz) and even some of the factory overclocked 7800 GTX's that we tested. This is equivalent to the performance that we would have seen at a 462MHz overclock. We did this without any special cooling systems, and the overclocking potential of these cards could be yet one more reason to choose the GT over the GTX right now. Buying a cheaper card and squeezing more performance out of it is maybe a better option than spending the extra money. But we have to say, as always, overclocking is risky and varies between cards, so if you plan on doing some overclocking yourself, we recommend paying very close attention to the warranty offered by the manufacturer.

The Card Performance Tests
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  • Leper Messiah - Thursday, September 1, 2005 - link

    I am SO buying one of these to upgrade my 9800np. The thing is starting to die in warhammer 40K and BF2, and my resolution sweet spot is 1600x1200, which means I can max everything with this card and run fine.


    I cool my 9800np with a zalman VF-7000 Al-Cu, or whatever it is...you know what I mean. I wonder if that will fit on there, would be nice to see a 480/1300 or something with my BGA ramsinks...
    Reply
  • blckgrffn - Friday, September 2, 2005 - link

    Apparently the 7800GT cards are too cheap to warrant Nvidia requiring a temperature sensing fan like the 7800GTX cards. How about that.

    *owner of a BFG 7800GT from Dell for $345 w/25 pack spindle of CD-R's :)
    Reply
  • NullSubroutine - Wednesday, August 31, 2005 - link

    Do we have to request 1280x1024 benchmarks still? I have to believe that alot of us out there have 19" lcd's that run native(max) at this res, so we dont really care what the speeds are at 16x12. Reply
  • n7 - Thursday, September 1, 2005 - link

    NullSubroutine: There is a reason why AT doesn't bother testing at 1280x1024.

    With a 7800 series card, nearly all games are CPU-limited, meaning there will be basically no difference in performance, since the CPU is holding everything back.

    Something many people fail to compregend is that the 7800s aren't really necessary if you don't have a 1600x1200 monitor or higher.
    Reply
  • Rocket321 - Wednesday, August 31, 2005 - link

    I think reviewing 2-3 cards per article would be best. That way we don't wait weeks for a huge roundup, and we also get to see the aspects of multiple cards at the same time. I don't mind the individual reviews either, but the first one is always less useful and the last one tends to be the most useful due to having more comparisons.

    --Rocket321
    Reply
  • Houdani - Wednesday, August 31, 2005 - link

    I'm city folk, and don't have an ounce of cowpoke in me, but that won't stop me from expressing an opinion of what I think life is like out on the range.

    When herding cows, the preferred method is to gather them all up and move them as a group. In other words, ROUNDUP! Sure a stray bovine might wander off, in which case you may ride out and bring back that individual, but generally speaking it's best to round all the cows up en masse and move them as a collective group.

    Likewise, when herding video cards, the preferred method is...[wink]
    Reply
  • UltraWide - Wednesday, August 31, 2005 - link

    How come the 7800GT is so noisy compared to the 7800GT-X.

    I did notice my BFG 7800GT is too dang loud. Maybe I should return it and get a 7800GTX???
    Reply
  • Marlowe - Thursday, September 1, 2005 - link

    A friend recently bought a Gigabyte 7800 GT and that's very noisy as well! Looks like the same cooler. Mounting a Zalman vf700cu would fix it. Anybody got cards from other brands? Post in! Reply
  • photoguy99 - Wednesday, August 31, 2005 - link

    Is there any conclusion on if this is true?

    Didn't see if the benchmarks used the driver that only reviewers have.

    According to the "reliable" source below, best case is you will lose 3% performance in high quality modes.

    http://www.theinquirer.net/?article=25820">http://www.theinquirer.net/?article=25820
    Reply
  • Live - Monday, September 5, 2005 - link

    I think Derek and/or Josh really should write something about this. Since it really invalidates the HQ benches and puts questions on the review process here at AnandTech. Why wasn’t this spotted when the original reviews came out? If ATI has something like this in there upcoming products I would sure like to know when I read the review here at AnandTech.

    Hexus has a write up and an apology.

    http://www.hexus.net/content/reviews/review.php?dX...">http://www.hexus.net/content/reviews/review.php?dX...
    http://forums.hexus.net/showthread.php?t=53394">http://forums.hexus.net/showthread.php?t=53394
    Reply

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