AMD Radeon HD 6990 4 GB

The Radeon HD 6990 is the flagship, high-spec model in AMD's 6000 series. At 30 cm long, this beast features two graphics chips that are similar to the one used in the HD 6970. We therefore can't help wondering how much power this monster card consumes, whether we'd better invest in some noise-reducing headphones and, above all, whether it can match the NVIDIA GeForce GTX 590. Read on for answers to all these questions and more.

Size, Noise and Heat

At over 30 cm de long, the Radeon HD 6990 won't fit into all computers and tower cases. Together with its predecessor (HD 5970), it has to be one of the biggest graphics cards that we've ever seen yet. That's no doubt due to the fact that is has two built-in graphics chips ... which also happen to get very hot.

As a result, this graphics card is very noisy, both when idle and when working hard. In fact, the GeForce GTX 590 seems really quite quiet compared to this one. AMD evidently hasn't managed to equip its power-packed model with an effective enough cooling system.

A Two-in-One Graphics Card

One original thing about the Radeon HD 6990 is that it has two different modes that can be selected using a little switch on the side of the card. The first mode, known as '375W' mode, is actually the maximum thermal design power (TDP) of the card. The second, known as '450W' mode, pushes the clock speeds a bit higher and also makes the card get a fair bit hotter.

Beware though—the card comes with a sticker covering the switch. In fact, AMD doesn't recommend users switch to 450W mode as this invalidates the product warranty. We, however, think it's pretty unbelievable (and not in a good way!) for a manufacturer include an option that's not covered by the product warranty. Whatever next?

Power Consumption

When idle, our test computer consumed 120 watts when loaded with the Radeon HD 6990, no matter which of the two operating modes we selected. That's already not very good, but it obviously gets even worse when you start playing games!

When gaming in 375W mode, we measured a consumption of 525 watts, rising to no less than 585 watts in 450W mode. These readings place the 6990 both below and above the GTX 590 with its 557-watt reading. In any case, a power source of over 600 watts is highly recommended.

Gaming Performance

No matter which mode you decide to use, this card offers top-notch performances and easily outdoes the NVIDIA GTX 590 (by 3% to 5% on average). It's therefore a perfect choice for gamers who are geared up for 3D gaming or who want to game over several monitors. Compared with AMD's former twin-GPU card, the Radeon HD 5970, this card is 20% more powerful.


All in all, the Radeon HD 6990 performs better than the NVIDIA GeForce GTX 590 when it comes to pure performance. Those performances do come at a price, however, as this card makes more noise and consumes more power in an equivalent computer set-up. That said, this type of card is only ever really aimed at a certain type of customer—fans of 3D or multi-screen gaming. Other users would probably be better off sticking to a graphics card with just one built-in processor.

Graphics Cards: Performance Index Tables