The hardware

Can you spot the CrossFire board?

Top of the Radeon X1800 CrossFire

Bottom of the card

Radeon X1800 CrossFire card

You’d be hard-pressed to spot any physical differences between ATI’s Radeon X1800 CrossFire card and a plain-jane Radeon X1800 XT 512MB. ATI has used the exact same board design, with the sole additions being the seven chips which comprise the compositing engine, and the VHDCI connection which lies alongside the card’s dual-link DVI connector (the Radeon X1800 CrossFire card also loses the S-Video connector present on X1800 cards). These chips lie just underneath the card’s fan. Power circuitry and cooling remain unchanged from the regular Radeon X1800 XT 512MB.

It’s the cooling in particular that you’re going to be most concerned about when running two X1800 cards in CrossFire mode. As you know by now, ATI outfits the Radeon X1800 XT 512MB with a massive dual-slot cooler. This means that the clearance between the X1800 CrossFire Master Card and its Radeon X1800 Slave card may be just a few millimeters. ATI’s own RD480 “Halibut” reference motherboard suffers from the same problem.

Connectors up close

Fortunately, due to the design of the X1800’s cooler, this shouldn’t be too much of a problem. You see, the card gets fresh air from the right side of the graphics card, rather than the top of the card (which is where most cards get their air from). The X1800’s blower-style fan sucks the air inside a ducted plastic enclosure, across the card’s massive copper heatsink, and ultimately the hot air is exhausted outside your system’s case. Therefore, even though the bottom X1800 card blocks the top X1800 card, the card on the top won’t overheat. We were able to run our Radeon X1800 CrossFire system for hours non-stop without any problems, despite the fact that the PCI-E graphics slots on our ASUS A8R-MVP CrossFire motherboard were barely separated. Of course, if you block the side of the card, that’s a totally different story.

The only exception to this rule is the Radeon X1800 XL, but more on this later.

Unfortunately, ATI still relies on a massive dongle to connect the Radeon X1800 CrossFire card to its slave X1800 board. The cables on the dongle are thick and fairly stiff, so bending them at the awkward angles required to connect everything properly for CrossFire to work is a little difficult. It doesn’t require SuperMan strength or anything, but it’s a lot less elegant solution than NVIDIA’s SLI cable. Once you’ve got everything connected properly, you’ll then want to use a small screwdriver to the VHDCI connection to the X1800 CrossFire master card. Then, once that’s done, boot your system up, install the graphics driver for the second graphics card and a magic “CrossFire” tab will appear under the 3D section of the Graphics Settings tab in CATALYST CONTROL CENTER. From there, click “Enable CrossFire” and voila, you’re done!

The whole process isn’t quite as polished as NVIDIA’s SLI, but still, if you’re an experienced computer builder installing and setting up a CrossFire rig shouldn’t be too difficult. The most confusing aspect of the whole procedure is the wide variance between the CrossFire motherboards. Some CrossFire boards require a transposer card to sit in the unoccupied PCI-E graphics slot when running in single card mode, while others (DFI) don’t. The location of the primary PCI-E graphics slot also varies depending on the motherboard, on DFI’s CrossFire board the top PCI-E slot is the primary slot you’ll install the Radeon X1800 CrossFire board, whereas on both the ATI and ASUS boards the bottom PCI-E graphics slot is the primary slot. In the grand scheme of things, these are minor quibbles, but we do find it a little ironic that after bashing NVIDIA’s SLI selector card ATI’s own RD480 reference board requires a tranposer card of its own.