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Nearly a year after nVidia won graphics enthusiasts over with its SLI dual-graphics-card technology, ATI is rolling out its own high-end dual-card platform. Our tests of preproduction boards show that the new technology, dubbed CrossFire, has promise but is plagued by design limitations and--so far--lackluster performance.

Like nVidia's SLI, CrossFire requires a special dual-slot motherboard. ATI advises buyers to use as-yet-unreleased motherboards based on its own Xpress 200 chip set (we ran our tests on a reference motherboard supplied by ATI). But ATI says motherboards based on Intel's 955X chip set with two x16 PCIe slots should also work satisfactorily.

To make ATI's dual-card scenario fly, you'll need one of its existing 850- or 800-series Radeon graphics cards (to act as a slave) and a new CrossFire Edition card (to function as a master). We tested a preproduction, high-end ATI Radeon X850 XT CrossFire Edition, in tandem with a Radeon X850 XT. The master card includes a compositing chip and a special DVI input for connecting the two cards via an external cable. This approach is inferior to nVidia's, which uses an internal SLI bridge clip to connect the two cards.

Even though both Radeon X850 XT graphics cards support 2048 by 1536 resolution when running solo, their maximum resolution in the dual-card setup was just 1600 by 1200. And the refresh rate sank to an eyestrain-inducing 60Hz; that's fine for an LCD but entails considerable flicker in a CRT. ATI says that these limitations shouldn't affect the vast majority of users, and anticipates that the issues will vanish in the next generation of CrossFire Edition cards.

We also found CrossFire's performance numbers wanting, especially compared with results from a solo version of nVidia's top-of-the-line card. Our PC World Test Center evaluation found that the dual-card Radeon X850 XT setup generally outperformed the single X850 XT, but usually trailed our speedy GeForce 7800 GTX reference board.

For example, in our Far Cry test at 1600 by 1200 resolution with antialiasing turned off, the ATI dual cards posted 81 frames per second. That beat the single X850 XT's peak of 75 fps; both lagged behind the GeForce 7800 GTX's 84 fps.

With antialiasing turned on, the nVidia card's lead in Far Cry grew significantly, reaching 51 fps, versus the single Radeon X850 XT's mark of 22 fps and the dual cards' 27 fps.

The GeForce 7800 GTX also bested both ATI models in our Doom 3 test run at 1600 by 1200 without antialiasing. But with antialiasing on, the dual X850 XT setup posted 64 fps versus 49 fps for the GeForce 7800 GTX and 35 fps for the solo Radeon X850 XT.

Postpone Upgrades

You may be eager to salvage your investment in a high-end ATI Radeon 800a??series card, but we can't recommend moving to CrossFire at this point. For top graphics performance and resolution, a board based on the nVidia GeForce 7800 GTX chip is your best bet. Still, we aren't ready to cross out CrossFire altogether: It could be more exciting when paired with ATI's next-generation cards, which should ship by the time you read this.