It was probably one of ATI's longest dry spells last year when they were long overdue for their DirectX10 card and when it finally did arrive the Radeon HD 2900 XT used far too much power and was an underwhelming performer compared to Nvidia's best. Luckily they came back strong last November with the Radeon HD 3870 and 3850 which performed excellently in the mid-range but unfortunately they still weren't able to claim the top spot. That has all changed with the Radeon HD 3870 X2 which combines two GPUs on a card in a way which we haven't seen previously.

For a few years now companies such as Gigabyte and Asus have experimented with putting two video cards together  to allow SLI or Crossfire without the need for two PCI-Express slots or an SLI or Crossfire chipset. These however weren't always the most eloquent solutions, incredibly large, hot, and with driver problems. In late 2006 Nvidia was the first to release a dual video card officially called the GeForce 7950 GX2 which glued two 7900 series cards together to enable SLI performance from a single PCI-Express slot. Unfortunately, the 7950 GX2 had issues with certain games either not working with SLI or crippling performance far worse than a single card. Being two months before the DX10 GeForce 8800 GTX which crushed it's performance didn't exactly help either.

The Radeon HD 3870 X2 does what the 7950 GX2 did but starts in a more efficient manner. Two 3870 GPUs are onboard the same PCB, not two PCBs stuck together as with Nvidia, connected by a PCIe 1.1 bridge to allow the two 3870. As you might know 2.0 chipsets were recently released but we don't believe this will have an impact on performance and the card should have more than enough bandwidth.

The card is built off the same 55nm manufacturing process as the 3870 and 3850 but features about double the transistors and other specs. 320 stream processors are now 640 with the 3870 X2, 32 texture units from 16, and 1GB of RAM from 512MB. The core clock speed sees an increase to 825MHz more than 775MHz standard clock speed of the Radeon 3870. Unlike the core speed the RAM runs at 1.8GHz effective speed over the higher 2.25GHz of a normal 3870.

As stated earlier a Crossfire chipset is not necessary for the cards to work and addition you don't need to enable Crossfire as you needed to enable SLI with the 7950 GX2s in the drivers. Of course games must support Crossfire or SLI in order for both cards to work properly and there have been some problems in the past with Nvidia more often than not in the lead with SLI titles. That said though ATI was a little late to the game with Crossfire, in all of the latest games we played we didn't run into any situation where Crossfire was not working. ATI has also resolved an issue with multi-GPUs with the Radeon 3870 X2 where multi-monitor support would not work with Crossfire or SLI enabled which is now fixed. One problem that does remain though is that currently two Radeon 3870 X2s will not work together for essentially quad crossfire but AMD says to expect something in March.

The card is naturally larger than a single 3870 as you might expect with two GPUs on the same PCB at about 10.5" and comparable in size to a GeForce 8800 GTX Ultra so the size is reasonable for most looking for a card this powerful. Unlike the Radeon 3870 there's a large heatsink covering the entire card to produce better cooling and a slightly larger fan. The card uses a 6-pin PCI-Express power connector and also an 8-pin PCI-Express power connector which they introduced with the 2900 XT. The eight pin is only necessary if you plan to use AMD Overdrive with the card, otherwise two six pin connectors will be fine.

Let's move onto our test system specs.