ATI Radeon X1800 XT CrossFire Edition

ATI Radeon X1800 XT CrossFire Edition

X1800XT_CF.jpgATI’s CrossFire technology finally gave ATI a dual-GPU solution. And even as we greeted the Radeon X850 XT CrossFire Edition with a barely stifled yawn, we held out hope that the X1800 XT CrossFire Edition would help the company advance down the field. No such luck.

This is not to say that ATI has completely fumbled the ball: A single 512MB X1800 XT is certainly fast, and pairing one with a CrossFire master card boosts performance anywhere from 24- to 73 percent. It’s just that two X1800 XTs running in CrossFire mode deliver benchmark results that are well behind a pair of nVidia’s 512MB GeForce 7800 GTXs in SLI. And now that nVidia has figured out how to run four GPUs in a single system (turn to the QuickStart section of this issue for the full story), nVidia has moved the goal posts even further.

We think at least part of the performance shortcoming can be attributed to ATI’s own core-logic chipset. We benchmarked the X1800 XT CrossFire solo first in our default test bed—an nForce4 system (an Asus A8N-SLI Deluxe motherboard, a 2.6GHz AMD Athlon 64 FX-55, and 2GB of DDR400 RAM)—and then in an ATI Radeon Xpress 200 environment (using Sapphire Technology’s Pure CrossFire PC-A9RD480 motherboard with an identical CPU and RAM). The card performed about two percent faster in the Asus motherboard.

If you’re not interested in AMD compatibility, ATI has also certified CrossFire for use in motherboards with Intel chipsets. ATI tells us it has also provided some of its system integrator partners with Catalyst drivers that support motherboards with nVidia’s nForce4 chipset. These special drivers are not available to the general public—and ATI doesn’t plan to release them.

Ignoring the negligible two-percent performance deficit between ATI and nVidia chipsets, both X1800 XT cards we tested lagged behind a single 512MB GeForce 7800 GTX running on the same motherboard. The stand-alone Sapphire card was 9.4 percent slower running 3DMark05, for example. Even though ATI’s OpenGL drivers have improved considerably, the Sapphire card ran nearly 22 percent slower than eVGA’s 512MB GeForce 7800 GTX card in Doom 3. Pairing Sapphire’s card with ATI’s X1800 XT master card boosted Doom 3 performance from 60.1fps to 87.2fps, but those frame rates are still 12fps slower than a pair of 512MB 7800 GTX cards in SLI.

ATI stacks up better when you compare two 512MB X1800 XT cards running in CrossFire mode to two 256MB 7800 GTX cards running in SLI. The eVGA eGeForce 7800 GTX KO boards we tested were not significantly faster than the ATI/Sapphire pairing in most tests, and the CrossFire system’s 3DMark05 score topped that of the SLI rig by nearly 3 percent.

Returning to the subject of drivers, ATI makes it easy for anyone to overclock an XT-class videocard right from within Catalyst Control Center. Once you’ve unlocked the card using ATI’s OverDrive tool, you can initiate an automated software routine that measures the system’s tolerance for overclocking and then sets up what it considers to be safe parameters for overclocking the GPU and memory. In our tests, OverDrive increased the card’s core clock from 594MHz to 624MHz, and the DDR3 memory’s clock speed from 693MHz to 797MHz.

ATI is also finally delivering on some of its promises about Avivo video technology. Our early hands-on experience with ATI’s X1000-series of videocards left us wondering if the Avivo demos we’d seen were little more than smoke and mirrors, but the latest Catalyst drivers have dissolved much of our skepticism: The X1800 XT’s HQV benchmark scores are now far superior to those of nVidia’s cards. And ATI tells us there are more improvements to come.

CrossFire’s external cabling arrangement still strikes us as a kludge, but if having a pair of videocards with a gigabyte of video memory is essential for your next rig, the X1800 XT CrossFire could be a worthwhile alternative to nVidia’s 512MB 7800 GTX boards, especially if ATI can actually produce the boards in any appreciable quantity (finding 512MB nVidia boards continues to be as futile as looking for bones in ice cream). And if video decoding is your crucial videocard application, ATI’s Avivo software is now the best solution—and it’s free (nVidia’s PureVideo software costs an additional $20).
Michael Brown

Month reviewed: March 2006

+ DUAL EXHAUST: Provides a solid upgrade path for X1800 owners. ATI makes overclocking nearly foolproof.

- EXHUAST FUMES: The CrossFire cables are a pain, and the cards aren't nearly as fast as those based on nVidia's technology.

Verdict: 8





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