Deeper with the GeForce 7900GTX
PCI Express x16 graphics cardsChipset GeForce 7900GTX 512 MB, 256 bit
The wait is finally over. Last month, NVIDIA launched their newest generation of graphics chips - the GeForce 7900. Just like the previous generation, there are two SKUs based on this chip: the high end GeForce 7900GTX and the more affordable GeForce 7900GT. Despite rampant speculation of a 32 pipeline graphics chip, the GeForce 7900GTX remain a 24 pipeline card, much like the GeForce 7800GTX. In fact, most of the specification between the two is pretty much the same, except for core and memory clocks. NVIDIA seems to be taking a more conservative approach this time around, no doubt not wanting to repeat what happen to the GeForceFX series.
The most significant changes on the GeForce 7900 series seem to be cost / production related. Not only did NVIDIA managed to shrink the die size of the chip (thus keeping production cost down), they were also able to throw out some transistors from the die and save more space in the process. It's no wonder that cards using this chip are selling at much lower prices than what they're charging for the GeForce 7800GTX at launch. No doubt, this is a calculated move to maintain and expand market share. Archrival ATI's X1900 based chips have a much larger die, so to counter this move, ATI have to cut their profit margins to keep their parts competitive.
Of course, while price is an important factor in any hardware purchase decision, most gamers still put performance first before everything else. However, unlike a few years ago, gamers nowadays are more aware of graphical features such antialiasing and anisotropic filtering. If the cards are fast enough (or priced high enough), it must deliver both performance and image quality. This is one area that NVIDIA seem to be 'lacking' - antialiasing usually comes at a significant drop in frame rates on NVIDIA cards. So, imagine how our ears perked up when NVIDIA claimed that the GeForce 7900GTX have much less performance penalty than the GeForce 7800GTX when running with antialiasing and anisotropic filtering enabled.
While moving to a smaller process (0.11 to 0.09 micron for the GeForce 7900) allowed manufacturers to reduce cost, there's no point of claiming the resulting product a new generation if there are no performance increases. Thankfully, clock increase is a by product of moving to a smaller process. With the same design and architecture, higher clocks (usually) means higher performance. Unlike the previous generation, the GeForce 7900GTX is clocked much higher than its successor. The reference specification is 650 MHz for core and 800 MHz (1600 MHz effective) for memory. In comparison, the GeForce 7800GTX ran at 430 MHz core and 600 MHz (1200 MHz effective). If you're paying attention, you'll probably notice that the GeForce 7900GTX memory clock is actually lower than what's on the monster that was the GeForce 7800GTX 512 - 1700 MHz. While its memory clock is slower, the GeForce 7900GTX no doubt has a much higher core clock - a 100 MHz difference to the 550 MHz of the GeForce 7800GTX 512. With that high a core clock, it seems odd NVIDIA didn't push the memory as high as they can go. Some have cited cost as the reason, but NVIDIA did mention they improve antialiasing performance on the GeForce 7900GTX. So, did they (finally) made some changes to the GeForce 7800GTX design? Maybe the GeForce 7900GTX don't really need that high memory clock. it will be interesting indeed to see just what NVIDIA tweaked on the GeForce 7900GTX.
Image Quality Comparison
For the launch of the GeForce 7900GTX, NVIDIA have updated their Forceware driver to version 84.21. In addition to several bug fixes and additional support for new cards, these drivers also provide some performance updates, particularly for F.E.A.R. Normally, any performance updates are good, but we're a little skeptic because of what NVIDIA have been caught doing in the past. Concerns about optimizations may not be that unfounded, as 3DCenter and Elite Bastards found out in their articles (which you can read here and here). So, before moving on to the performance evaluation, we took some time examining the screenshots and performance from these drivers on a GeForce 7800GTX.After testing these new drivers, we found there's no reason to worry about questionable optimizations. Performance under High Quality and Quality settings are where they should be and turning off performance optimizations related to anisotropic filtering work as intended. Visually there's hardly any difference between these drivers and the previous versions, but let's take a look at the screenshots just to make sure.
Below you'll see several screenshots from the GeForce 7800GTX and 7900GTX. To keep things short, we skipped the non AA and AF screenshots, so it's all 4x AA with 16x AF.
Call of Duty
GeForce 7800GTX
GeForce 7900GTX
There are no differences between the screenshots, so the increase in performance seems valid. Call of Duty is one game that also experience an increase in performance with the new drivers - a 10 percent increase running without AA and AF. With AA and AF enabled, the increase is negligible, mostly 3 - 5 fps from a total of above 150 fps (1 percent). So, from the looks of it, NVIDIA managed to squeeze more performance from system limited functions, rather than just memory or rendering tweaks.
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