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ATI's Radeon X700 XT graphics card

The red team answers

THE STRUGGLE FOR THE upper hand in the graphics market has never been tighter than it is right now between ATI and NVIDIA. The two companies both made giant strides forward this past spring with the introduction of new graphics chips boasting over twice the power of the previous top-of-the-line models. These new GPUs, the Radeon X800 and GeForce 6800, were very evenly matched when they arrived, although ATI's Radeon X800 had a slight lead in performance overall. The race has only tightened as NVIDIA has refined its drivers and snazzy new games like Doom 3 have arrived.

The contest, however, is just beginning. Sure, some folks buy those $399 graphics cards, but I get a nosebleed just thinking about it. The real action is down under $200, where those of us who don't host our own reality shows can afford to play. Two weeks ago, NVIDIA pulled the wraps off of the GeForce 6600 GT, a $199 product that offers performance superior to last month's $299 graphics cards, causing us to proclaim the thing "freaking awesome." Today, ATI responds with the launch of its own new mid-range GPU, the Radeon X700 XT. Derived from the Radeon X800, the X700 series offers all the fancy-schmancy new features of its big brother, including improved pixel shaders and a revamped memory controller. How does the Radeon X700 XT stack up against the GeForce 6600 GT? Read on to find out.

The Radeon X700 family
The time-honored tradition in designing a mid-range graphics chips goes something like this: saw your high-end product in half, give it half the memory and half the memory bandwidth, and you're pretty much set. (Sure, there's engineering work to be done in order to make that happen, but that's the basic procedure.) This approach has become easier over time as graphics chips have grown in terms of internal parallelism and as engineers have made their chip designs more modular. The ATI R420 (Radeon X800 series) and NVIDIA NV40 (GeForce 6800 series) chips are excellent examples of this wider, more modular approach. Both chips segment their sixteen internal rendering pipelines into sets of four. These "quads" lend themselves to internal reshuffling, as twelve-pipe variants like the Radeon X800 Pro and GeForce 6800 demonstrate.

In the case of the chip behind the Radeon X700 series, the RV410, one would expect ATI to slice an R420 into two and call it a day. That's not exactly what happened when ATI designed the RV410, however. Yes, ATI did give the RV410 a pair of four-pixel-pipeline quads so that the RV410 is an eight-pipe chip. Rather than cut the RV410 down further, though, ATI elected to retain all six vertex shader units from the X800 series, giving the RV410 a potential edge on the competition. (The NV43 chip that powers the GeForce 6600 series has only three of NVIDIA's vertex shader units, but those units don't necessarily deliver the same performance, clock for clock, as ATI's.)

ATI also held the line on memory, reducing the width of the memory interface from 256 bits in the R420 to 128 bits in the RV410, but keeping 256MB of memory on the cards. At least, that was the original plan. ATI initially told us all three flavors of the Radeon X700 would come with 256MB of memory, but after seeing NVIDIA's GeForce 6600 GT at $199 with 128MB of memory, the red team apparently changed its mind. When our review unit arrived, it was a version of the X700 XT with 128MB of memory and a $199 price tag. Here's the rundown on the complete Radeon X700 lineup.

  Core clock (MHz) Pixel pipelines Memory clock (MHz) Memory bus width (bits)On-board memorySuggested
Radeon X7004008600128128MB$149
Radeon X700 Pro4208864128256MB$199
Radeon X700 XT47581050128128MB$199
Radeon X700 XT47581050128256MB$249
ATI set the clock speeds on the lower end versions of the Radeon X700 some time ago, but they held off on setting final speeds for the X700 XT until they got a look at NVIDIA's GeForce 6600 GT. The final clock speeds for the X700 XT are 475MHz for the graphics chip and 525MHz for the memory—25MHz less than the competing NVIDIA on the core clock, but 25MHz higher memory speeds.

Like the competition, the Radeon X700 family will first be available as PCI Express cards, in part because the RV410 GPU has a PCI Express interface onboard, and in part because the big PC makers like Dell already prefer to sell PCI Express-based systems. ATI says Radeon X700 Pro PCI-E cards will begin shipping immediately to the big PC manufacturers, while the other X700 PCI-E cards should be ready to roll some time during October. No firm date has been set yet for online or retail availability of these cards to consumers. Similarly, ATI will eventually introduce AGP versions of the Radeon X700 that use a bridge chip to allow the RV410 GPU to talk to AGP-based systems, but the company hasn't said yet when those cards will arrive.

The Radeon X700 XT The Radeon X700 XT card has dimensions very similar to the Radeon 9600 XT that preceded it, and it's very nearly the same size as a GeForce 6600 GT. The X700 XT's cooler is similar in size to the 6600 GT's, as well, but the X700 XT's cooler is an all-copper affair that's much, much heavier.

You can see the big rectangular vacancy on our X700 XT review unit in the top picture above. That's where ATI's Rage Theater chip will reside, to provide video input capabilities on cards with a VIVO option. ATI says some "made by ATI" cards in North America will be available with VIVO. Notice, also, the four blank pads on the underside of the card where memory chips would generally reside. This is a 128MB card. I'd expect 256MB cards to have memory chips populating those spots.