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AMD's Radeon HD 5970 graphics card

It doesn't get any more extreme than this

We used to be friends, you know, back in the day. Me and Fatal1ty, I mean. We worked at the same ISP, him taking customer calls on the support front lines and me in the back room, keeping the network running. He came to me when he couldn't fix a problem. We even played Quake together, before he became the biggest gamer in the world over the successive 18 months or so and I became, well, a cable modem admin.

Sometimes I look back and think, had circumstances been different—had nature, for instance, given me a vastly superior set of skills, abilities, looks, social graces, age, and intelligence—that I could have had the same sort of success that he has. But then I wonder: could I have handled it? Not the pressure of competition or any of that, but the sheer extremeness of being so extreme. Drinking the energy drinks, wearing the bright colors, the hair gel. And I realize, I probably could not have.

Had I somehow managed it, though, without spontaneously combusting, I expect that this new video card from AMD, the Radeon HD 5970, would surely have become my weapon of choice.

The Radeon HD 5970

AMD offers its competition a sip of Hemlock
In spite of its singular name, the Radeon HD 5970 is in fact a dual-GPU graphics card in the tradition of the Radeon HD 4870 X2. Codenamed "Hemlock" during its development—or at least during its pre-launch marketing stage—the 5970 sports two of the Cypress GPUs that power the Radeon HD 5870. Each GPU has its own 1GB bank of GDDR5 memory, and the card itself is longer than a fourth-grade piano recital, measuring out to 12.16" or 309 mm. Here, have a look at how the 5970 measures up against some common varieties of graphics cards.

From left to right: GeForce GTX 295, Radeon HD 5970, Radeon HD 5870, Radeon HD 4890

At 9.5", the Radeon HD 4890 looks positively puny by comparison. Even the considerable 10.5" span occupied by the GeForce GTX 295 looks way less extreme. The crazy thing is that the 5970's Batmobile-inspired plastic shroud extends roughly half and inch past the end of the board itself—and its primary purpose is to look cool.

AMD points out that the 5970's length is compliant with the ATX spec, but we haven't seen a video card this long for many, many moons. I fear many PC cases these days aren't really built to accommodate such a beast, especially the mid-towers. The bottom line here is that you'll want to measure for clearance in your own case before hitting the "Buy" button at your favorite online retailer. Then again, if you've ponied up for an Obsidian, you surely need not worry.

Dual dual-link DVI ports flank a mini-DisplayPort, er, port

Due to the need to free up an entire slot backplate for the cooler's exhaust, the 5970 has a different port config than the rest of the Radeon HD 5000 series. The HDMI port has been deleted, while the DisplayPort output has been hit with a shrink ray and reduced to Mini size. Despite the changes, AMD says the 5970 can still drive up to three displays simultaneously, and 5970 cards will ship with a pair of adapters: one that converts Mini DisplayPort to regular DisplayPort, and another of the DVI-to-HDMI variety.

A combo of six- and eight-pin connectors provides power

As the combination of six- and eight-pin power plugs portends, the 5970's max power draw is rated at 294W, just under the 300W limit imposed by the PCIe spec. The good news on the power front comes at idle, where the 5970 inherits the very nice reductions in power draw achieved by the Cypress GPU and its memory controller. To that, this card adds another wrinkle: when it's not needed, the second GPU enters a low-power sleep state (AMD likens it to the ACPI S1 state, if you must know), which should blow Al Gore's skirt up. As a result, the 5970's idle power draw is rated at 42W.

Two GPUs, but just a single external CrossFire connector

The Cypress GPUs on either side of the PLX PCIe bridge chip

The 5970's dimensions and peak power draw are so ample because the card has to accommodate two copies of what is currently the fastest GPU on the market. This really is "CrossFire on a stick," as we like to say, and the performance potential from such a beast is naturally quite considerable. Situated between the two GPUs in the picture above, under a metal cap, is a PCI Express switch chip from PLX, the same model used in the Radeon HD 4870 X2. This chip can support a trio of PCIe x16 links: one to each of the GPUs and a third to the PCIe x16 slot in the host system.

Like any two GPUs in a CrossFire pair, the 5970's Cypress chips communicate with each other by means of those PCIe links and via a dedicated CrossFire interconnect, as well. Gone is the GPU-to-GPU "sideport" connection that was present on the 4870 X2. AMD says improvements to its drivers and to the performance of its CrossFire interconnect have rendered the sideport link unnecessary, even though the CrossFire interconnect's physical bit rate, at 7.92 Gbps, remains similar.

Although the magic is all taking place on a single card, the 5970 is subject to the same limitations as any multi-GPU solution. That means you won't always be able to take advantage of both GPUs in a new game until you've installed a driver update with a CrossFire profile for it. Also, you can expect to see something less than twice the performance of a single GPU, because multi-GPU performance rarely scales up perfectly.

Still, we must admit that AMD has made great strides in its multi-GPU support since committing to these dual-GPU cards. The latest bit of evidence on that front is the fact that the 5970's release drivers will support AMD's Eyefinity multi-monitor gaming capability. This is a first, and the support currently only extends to 22 games. We haven't yet had time to try it out for ourselves, either. Still, it is a positive sign.

Speaking of signs, the one in the store next to the 5970 will read "$599.99" or thereabouts. That's not cheap, but it's somewhere between the price for two Radeon HD 5850s and two Radeon HD 5870s, so it has its own cruel logic. This is not a bargain-bin item by any stretch. The larger question is whether you'll be able to buy one at any price, given the shortages we've seen on Cypress-based 5850 and 5870 cards, coupled with reports of yield issues at TSMC on 40-nm chips. When we quizzed AMD about 5970 availability, they could only say they expect the 5970 to be selling today at multiple online retailers and that supply "should be steady" through the holidays. Whether it'll be a steady drip or a steady torrent remains to be seen, but I'm betting on the drip at this point.