ATI Radeon HD 3870 X2 Hands-On

The ATI Radeon HD 3870 and HD 3850 are both fine cards and are compelling values at their respective sub-$300 and sub-$200 price points. However, PC enthusiasts were expecting more when AMD first introduced its ATI Radeon HD 3800 lineup late last year, namely a high-performance card that could take on Nvidia's GeForce 8800 GTX. AMD didn't have an answer for the GTX last November, but it did promise a dual-GPU card for early 2008: the ATI Radeon HD 3870 X2. Today we take our first look at AMD's new dual-GPU video card.

The card itself looks much like any other single-fan, double-wide video card, but a close side examination reveals two separate heat sinks for the card's dual GPUs (and a third, smaller heatsink for the bridge chip). The GPUs are basically Radeon HD 3870 cores with improved power efficiency and higher clock speeds. Each X2 graphics chip runs at 825MHz compared to 775MHz for a single Radeon HD 3870. The card comes with 1GB of GDDR3 memory, 512MB for each GPU. The X2 performance will definitely be better than a single Radeon HD 3870, but not quite double the power. Expect to lose some performance due to the overhead involved in getting two GPUs to work in tandem. The X2 also has slower 1.8GHz GDDR3 memory compared to the Radeon HD 3870's 2.25GHz GDDR4 memory.

The Radeon HD 3870 X2 shares the same features as the rest of the cards in the Radeon HD 3800 series family. That means you'll get DirectX 10.1, and full hardware-accelerated HD video decode. The DirectX 10.1 support is a forward-looking feature that will benefit you later down the line, but the HD video acceleration will help immediately with HD-DVD, Blu-ray, and all the major HD video file compression standards. The Radeon also has a built-in sound processor that allows the card to output full HDMI, both audio and video, directly to an external display device.

The Radeon HD 3870 X2 requires only a single video card slot, but you currently cannot run two cards together in CrossFire at this time. AMD has told GameSpot that it plans to offer X2 CrossFire support this March. The card also lacks PCI Express 2.0 because the special bridge chip that connects the card's GPUs together only supports PCI Express 1.1.

We recommend getting a 500W power supply for the X2. You will also want to make sure that the power supply has the right power cables for the X2's external power requirements. The card has one eight-pin socket and one six-pin socket, but the eight-pin socket will work with a six-pin cable.

We tested the $449 Radeon HD 3870 X2 against its closest price competition, the GeForce 8800 GTX. Both cards share the $400-$500 high-end range. We tossed in a Radeon HD 3870 CrossFire setup to see how the dual-card configuration compares to its single-card replacement. We also added a $1,000 GeForce 8800 GTX SLI system and a single $250 Radeon HD 3870 to show you what kind of performance you can get at higher and lower price points.

The X2 cruises by the GTX in Crysis and Unreal Tournament 3 but falls slightly behind in Call of Duty 4. We noticed that the X2 and CrossFire setup did not seem to offer any performance improvement over the single Radeon HD 3870 in our Call of Duty 4 test, which usually indicates some kind of multi-GPU setting snafu or plain old user error, but we determined that our level selection was the cause of the performance peculiarity. It appears that the intense firefight at the start of "The Bog" level in our Call of Duty 4 test doesn't allow the X2 or CrossFire systems to put up as many gaudy numbers as on the easier levels. The X2 showed a 60 percent frame rate improvement over the Radeon HD 3870 when we tested the opening sequence of an earlier mission.

AMD recently released a new driver to improve Crysis performance in Windows Vista. It appears that the drivers simply bring the Vista numbers more in line with Windows XP performance.

Call of Duty 4 issues aside, the Radeon HD 3870 X2 does appear to be a viable choice among the sub-$500 video cards. The X2 performed well compared to the GeForce 8800 GTX in our benchmark tests, justifying its status as AMD's flagship card. The X2 also has the HD video decode acceleration and HDMI support media fans demand. We had been worried about encountering multi-GPU related issues with the X2, but we can say that we didn't encounter any of those types of problems with the card, the graphics drivers, or game support. The Radeon HD 3870 X2 behaved like a single-GPU video card, and that's the way we like it.