Although partner cards share the same GPU and basic board design, manufacturers are free to play around with bundled software and extras, coolers, clock speeds, and of course, pricing. Factory "overclocking" has become particularly popular of late, with some manufacturers increasing core and memory clock speeds by as much as 25% beyond "default" speeds—a margin that can have more than just a modest impact on performance. Higher clock speeds don't always come cheap, of course, but they can go a long way toward making a card stand out. So can a great game bundle, a quieter cooler, or a lifetime warranty.
To get an idea of how different board manufacturers are approaching NVIDIA's GeForce 7900 series, we've rounded up a collection of cards from Asus, Biostar, BFG, and XFX. Read on to find out which offers the best performance, extras, and overall value.
The difference an X makes
NVIDIA's GeForce 7900 series spans two products: the 7900 GT and the 7900 GTX. Both rely on the G71 graphics processor, which is an optimized, die-shrunk derivative of the G70 GPU that powered the GeForce 7800 line. Since we're focusing on partner cards, we won't delve too deeply into the G71's attributes. For a more detailed examination of the chip's features, see our initial GeForce 7900 review.
We're looking at both GeForce 7900 GT and GTX cards, so it's worth highlighting the key differences between them. The GeForce 7900 GT and GTX both feature 24 pixel and eight vertex shaders, in addition to 24 texture units and 16 ROPs. In other words, both flavors of the GeForce 7900 have the same number of functional units for processing polys and pumping out pixels.
|Pixel shaders||Vertex shaders||Texture units||ROPs||Core clock (MHz)||Vertex clock (MHz)||Memory clock (MHz)||Memory bus width||Memory size (MB)|
|GeForce 7900 GT||24||8||24||16||450||470||660||256-bit||256|
|GeForce 7900 GTX||24||8||24||16||650||700||800||256-bit||512|
NVIDIA relies on a massive gap in clock speeds to differentiate the two. The GeForce 7900 GT's core runs at just 450 MHz—a full 200 MHz slower than that of the GTX. The G71's vertex shader runs a little faster than the core, and again, there's a difference between the GT and the GTX. While the GTX's vertex shader gets a 50 MHz boost over the graphics core, the GT's vertex unit runs only 20 MHz faster.
The clock speed disparity between the 7900 GT and GTX extends beyond the graphics chip. Memory clocks differ, as well, with the GT's memory running at 660 MHz by default and the GTX's clocked at 800 MHz. The GTX also doubles the GT's onboard memory to 512 MB, although both use a 256-bit memory bus.
Five twists on NVIDIA's reference design
We're comparing five different GeForce 7900 series graphics cards from four of NVIDIA's board partners. Each offers a unique mix of clock speeds, warranty coverage, and price. We'll cover each in more depth individually, but to kick things off, let's have a quick look at how they compare.
|GeForce 7900||Core clock (MHz)||Memory clock (MHz)||Memory size (MB)||Warranty length||Price|
|Asus EN7900GT TOP||GT||520||720||256||3 years|
|BFG GeForce 7900 GT OC||GT||475||680||256||Lifetime|
|BFG GeForce 7900 GTX OC||GTX||670||820||512||Lifetime|
|Biostar GeForce 7900 GT||GT||450||660||256||2 years|
|XFX GeForce 7900 GT XXX Edition||GT||560||825||256||"Double lifetime"|
BFG's GeForce 7900 GTX OC is the only GTX in the lot, and as you can see, its core and memory clocks are an improvement over those of a stock GTX. Clock speeds are more varied on the GT front, where Asus, BFG, and XFX each favor a different combination of core and memory clocks. XFX's XXX Edition is the most extreme case of factory overclocking, with higher core and memory clocks than any other GeForce 7900 GT. Biostar's 7900 GT is the only card running at stock speeds. That should make it an interesting performance baseline against which to judge the "factory overclocked" cards.
Although factory "overclocking" pushes core and memory clock speeds beyond the baseline defaults prescribed by NVIDIA, card makers fully qualify and validate cards at these higher-than-stock speeds. Manufacturer warranties cover these cards at their factory default clock speeds, too, regardless of whether those speeds go beyond what's considered stock by NVIDIA. Any real overclocking of the cardtaking it beyond the stock speed from the card makerwill still void your warranty, though.
Speaking of warranties, Biostar offers two years and coverage and Asus offers three, while BFG Tech provides a lifetime guarantee on its 7900 GT and GTX cards. XFX ups the ante a little with a "double lifetime" warranty that maintains coverage even when the card is on its second owner.
With the most extensive warranty coverage and highest clock speeds, it's not surprising to see the XFX XXX Edition's street price above that of other GeForce 7900 GT cards. According to XFX, the XXX Edition is actually in short supply. The card is only available from one online retailer in our price search engine, which could explain why the price is so much higher than more widely available GeForce 7900 GTs from other manufacturers.
Apart from the XFX card, only about $10 separates the rest of our GeForce 7900 GTs, which should make for an interesting comparison. The BFG 7900 GTX is considerably more expensive, of course, but its price is backed up by better performance and other perks that we'll explore in more depth momentarily.