Radeon HD 7990 And GeForce GTX 690: Bring Out The Big Guns

EVGA recently lent our German lab one of the GeForce GTX 690s we've had in the U.S. for months. The purpose? To pit against HIS' upcoming 7970 X2 and PowerColor's Devil13 HD7990, both dual-Tahiti boards vying to become the world's fastest graphics card.
A couple of weeks ago, our German office got an exclusive on HIS' new flagship graphics card, the 7970 X2 (notice that they're not calling it a Radeon HD 7990). Because we also have PowerColor's Devil13 HD7990 6 GB in our lab, along with a GeForce GTX 690 from EVGA, we're about to crown the fastest graphics card of 2012 right here and right now.
Will the outcome matter to you? Well, PowerColor's board is currently listed on Newegg for $1000, but it's out of stock. The HIS card doesn't even show up for sale online yet. Our sample was part of a small, limited-production run (we'll come back to this in the conclusion). Only EVGA's offering is sitting on store shelves. And while it also goes for $1000, making it too expensive for most folks, there's at least something to be said for availability, right?

With its factory overclock, PowerColor's Devil13 HD7990 6 GB comes very close to the GeForce GTX 690 in our performance-oriented tests. Meanwhile, HIS' 7970 X2, which was shown off at Computex, but not necessarily a sure thing, is finally ready. Elevated clock rates are supposed to make the HIS card the fastest graphics card, period. But do the benchmarks concur? Let's have a look at how these three boards stack up on paper first.

Radeon HD 7970 X2, Radeon HD 7990, And GeForce GTX 690
	HIS 7970 X2	PowerColor Devil13 HD7990 6 GB	EVGA GeForce GTX 690
Shader Units	2 x 2048	2 x 2048	2 x 1536
GPU Clock Rate	1050 MHz	925 / 1000 MHz	915 MHz +Turbo
ROPs	2 x 32	2 x 32	2 x 32
GPUs	2 x Tahiti XT	2 x Tahiti XT	2 x GK104
Transistors (Billion)	2 x 4.31	2 x 4.31	2 x 3.54
Memory	2 x 3 GB	2 x 3 GB	2 x 2 GB
Memory Bus	2 x 384-bit	2 x 384-bit	2 x 256-bit
Memory Clock Rate	1500 MHz	1375 MHz	1502 MHz

Technically, the HIS card looks like it holds a strong position. If those numbers translate into real-world performance, and if micro-stuttering isn't a problem for AMD, it could be our winner. Then again, we already saw in GeForce GTX 690 Review: Testing Nvidia's Sexiest Graphics Card that Nvidia put a lot of effort into creating a fast, svelte, and quiet offering in its GeForce GTX 690. That'll be a tough act to follow.

HIS 7970 X2: Can It Become The New King?

We first contacted HIS about its 7970 X2 during Computex, earlier this year, and followed the card's development after that. After beta testing a an early sample with the serial number of 7, we now have a production-ready card with the number 616. This is the version you should be seeing for sale soon, so we can finally share it with you.
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Our card has the same technical specifications and features as the final version, except for its somewhat-makeshift plastic cover.
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The black box containing the 7970 X2 is similar to what we've received other HIS cards in, so it should also be pretty close to the final version.
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HIS is employing a controversial triple-slot design, which consumes quite a bit of expansion space. The idea would be that a card like this one would save you from having to buy two dual-slot boards in CrossFire, yielding a net gain of one slot, though.
More room to work inside gave HIS' engineers space to address cooling aggressively. Note the two 95 mm fans centered right above the Tahiti GPUs.
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Up on top of the 7970 X2 you find three eight-pin power connectors. Each of those inputs is able to provide up to 150 W, necessary (and still not enough) to satisfy the card’s massive power requirements.
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A look at the bare board shows us that HIS split up the power supplies for each GPU, separating them on the PCB. PowerColor does not do this on its own design.
What the HIS and PowerColor boards do share in common, however, are six power phases for each GPU and two phases for each 3 GB bank of GDDR5 memory. HIS uses Magic R30 coils on its implementation, leading to less coil whine. This is a much bigger issue for the competition, unfortunately.
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HIS takes a unique approach to cooling. Instead of using one large heat sink across two GPUs, the company deploys two separate coolers. Each sits on top of its own GPU, and is controlled independently.
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The way this card was designed, its heat pipes run horizontally, while the cooler's fins are oriented vertically. We don't like this. Half of the heat blown through the sinks ends up on the motherboard. The other half gets blown out of the card's top. There are corresponding advantages, of course. Since heat isn't blown out the back of the board, your hard drives don't receive the brunt of the exhaust. More than likely, HIS expects its 7970 X2 to end up in chassis with side fans, but we aren’t so sure we agree.
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The visible dent you see in the shroud is there on purpose, due to a capacitor that was in the way. Our newer version of the card (the one that we benchmarked) doesn't have this dent.
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The 7970 X2’s two GPUs are connected to a Lucidlogix LT22102, a 48-lane switch configured into one 16-lane upstream port and two 16-lane downstream ports. Unfortunately, it's limited to PCI Express 2.0 signaling. As a result, the PCI Express 3.0-capable Tahiti GPUs are forced back to second-gen transfer rates. Do we see this as an issue? Not really. Modern graphics processors still don't fully saturate a 16-lane PCIe 2.0 link.
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Although our benchmark sample isn't representative of the final retail 7970 X2, it's fully functional. Once HIS has more to tell us about its official launch date and pricing information, we'll pass that information along.