AMD Radeon HD 6990 Review

Posted: August 23, 2011 in Tech Info

When we took a look at the reference version of AMD’s Radeon HD 6990, we found a board that was impressive on a number of fronts, though not all the impressions were positive. The HD 6990 builds in two full Radeon HD 6970 GPUs onto a single board, each with its own 2GB of frame buffer. In our initial testing, performance looked to be very fast, but the reference board was also pretty noisy under load.

So we waited to get a shipping board from one of AMD’s many board partners in order to formally review a real product. And we waited. And waited some more. (Bear in mind that availability of Nvidia’s GTX 590 isn’t much better.)

At last, XFX shipped us an actual retail Radeon HD 6990, so we’re finally able to render a verdict on AMD’s killer card. Before we dive into benchmarks and observations, it’s worth recapping the specs and features of the card, and its GPUs.

The Radeon HD 6990 has five total display connectors, though it does cut back on the variety compared to the HD 6970, with four Mini DisplayPort connectors and a single dual-link DVI connector. XFX includes a pair of Mini DP–to–single-link DVI adapters (one passive, one active) plus one Mini DP–to-HDMI adapter in the box. With two GPUs and 4GB of GDDR5, this is a big card—over 12 inches long. It also requires two 8-pin PCIe power connectors.

It’s also worth looking at core clock differentials. Nvidia reduces the core clock speed of its dual-GPU GTX 590 card by more than 20 percent, from 772MHz to 607MHz. By contrast, AMD lowers the core clock speed of the HD 6990’s GPUs by only about 6 percent. It could be that AMD’s GPUs are more power efficient, or simply that AMD is being more aggressive about its overall design. Given the HD 6990’s noise level under load, we suspect a little of both.

As with the reference card, the XFX card has that overclocking mini-DIP switch that allows you to push the clock speed up to 880MHz—the same core clock as a single-GPU HD 6970 card. However, XFX puts a giant yellow caution sticker over this switch. Given that rather dire warning, we tested the card at its default 830MHz clock speed.

Now that we understand a bit more about the key features, let’s look at performance.

AMD’s HD 6990 wins seven of our benchmarks, ties in one, and loses to Nvidia’s GTX 590 in the remaining three. The 6990’s maximum power draw is marginally lower. All of the games we tested support CrossFireX; if you’re running an older game that doesn’t support AMD’s dual-GPU technology, you’ll only see the performance of a single HD 6970. However, AMD’s done a ton of work with its drivers, and all the current-generation games we’ve tested get a solid performance boost.

On the other hand, the XFX HD 6990 is considerably louder at full throttle than the GTX 590. Clearly, AMD has some work to do with its cooling solution to reduce noise levels. Or maybe AMD is just pushing those 40nm-based 6970 chips a little too hard, even at the lower clock speeds. As you might suspect given the fan noise, the HD 6990 gets quite hot at full load, so you’ll definitely want a case with robust airflow.

The bottom line: XFX is shipping the fastest graphics card you can buy—that is, if you can find one. Availability is still very tight, and if you order one, expect it to be backordered for several weeks. It’s also quite hot and quite loud, so be aware of that before buying. And all that performance comes at a price—the HD 6990 is also the most expensive card you can get, with prices ranging from $700-$800 depending upon the seller.

Still, if you’re really looking for raw speed in a single graphics card—noise, heat, and price be damned—the HD 6990 is the frontrunner.

Via maximumpc.


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