AMD Radeon HD 6990 Review - PAGE 18

Temperature:

To measure core GPU temperature, MSI's Kombustor was used. The idle temperature was taken after leaving nothing running for up to 15 minutes. The load temperature was taken 15 minutes after starting Kombuster for Multi-Core graphics cards

When the HD 6990 was used with the default settings, the Vapor Chamber cooling solution efficiently cooled each GPU as the maximum temperature only reached 83°C. In the overclocked position though, the thermal solution was less efficient as each core hit 90°C at load.

Power Usage:

To measure power usage, a Kill A Watt P4400 power meter was used. Note that the above numbers represent the power drain for the entire benchmarking system, not just the video cards themselves. For the 'idle' readings we measured the power drain from the desktop, with no applications running; for the 'load' situation, we took the sustained peak power drain readings at the end of a 30 minute Kombustor run.

The power consumption for the HD 6990 is right where we thought it would be considering its higher than average TDP. This could be a potential downfall for the graphics card as it requires a substantial amount of power, even when using the stock 375W setting.

Conclusion:

AMD has a lot riding on the success of the HD 6990 as they have maintained the performance crown since the release of the HD 5970. To maintain their title AMD built their latest dual GPU graphics card around a 375W TDP, which allowed them to use dual Cayman XT based GPUs.  The Antilles graphics card also includes a total of 3072 ALUs, 192 Texture units and 64 ROPs. However, even with a high peak power rating some sacrifices had to be made, as the clock speed was slightly reduced to 830MHz. This slight reduction could lower the performance in comparison to dual HD 6970s in CrossFire, but in our testing it was still able to perform better than a CrossFire'd HD 6970 and HD 6950 in all but one benchmark. 

The HD 6990 had excellent performance across the board, but where it really excels is at running games at high settings and resolutions. This is due to the large 4GB frame buffer, which allowed it to scale very well up to 2560x1600. In our testing the only game where the HD 6990 was not able to maintain a constant 60+ frames-per-second rating (while at the highest resolution) was Metro 2033.

To increase the performance of the HD 6990 even further, AMD has pushed the thermal properties of the board to its limits by included an Uber mode switch. This is essentially an overclocking switch that when activated increases the GPU clock speed to 880MHz, further boosting the total compute power of the graphics card. With this setting the overall performance level was increased in all our benchmarks, but it comes at the cost of a 450W TDP and decreased thermal efficiency.  During our testing of the Uber mode, the HD 6990 reached temperatures up to 90°C. So, while this mode offers exceptional in game performance, it also produces more heat and consumes more power.

Where the "AUSUM" mode really impressed us was during our overclocking session, as the 450W TDP greatly increased the board's overclocking ceiling. In all we were able to raise the GPU clock speed to 1000MHz and set the memory at 5.6Gbps. With these settings, the HD 6990 had a total compute power above 6 TFLOPs! That’s an unreal amount of gaming power and it yielded hugely impressive results across all our benchmarks. However, to maintain the high clock speeds we did have to increase the fan speed to 75% rotation, which was quite loud.

The largest issue we have with the "AUSUM" option, however, is that using the setting will instantly void the warranty. While using the setting we were impressed with the results, but who is going to pay $699.99 and use a feature that voids the warranty instantly? Also, this ensures that the card will have less overclocking headroom for those that dont flip the switch. This is due to the voltage being at 375W, when in our testing the HD 6990 required the full 450W to run at 1000MHz.

Another aspect where the AMD HD 6990 stood out even from other cards in the series was with its support for Eyefinity. Out of the box, the Antilles graphics card has 5-way Eyefinity support. This gives the graphics card the ability to setup multiple display configurations and with the massive amount of compute power available, it is the best option available to run 3D applications across multiple displays. In addition, all Antilles graphics cards will ship with three display adapters that further increases the Eyefinity support.

Overall the HD 6990 smashed any expectations we had going into the review as it just dominated any other card in its path, including the current single GPU speed king, the GTX 580, and the dual GPU HD 5970. This makes Antilles the best available single PCB solution for high resolution gaming, but with such a high TDP the board requires a substantial power supply to run, can get extremly loud at high RPM and generate a massive amount of heat.

At launch the HD 6990 “Antilles” graphics card will have an MSRP of $699 USD. This is a hundred dollars more than the launch price of the HD 5970 and certainly more than we anticipated. Still, it costs slightly less two HD 6970 graphics cards, and it offers dual Cayman XT performance on a single PCB. So, if you're looking for the fastest graphics card on the market, the HD 6990 fits that title and more. Just make sure the rest of your system can handle this 375W monster!

Update:

After our initial testing of the HD 6990 we moved the graphics card over to a backup system that we were using to test new games for our benchmarking suite. We were able to complete testing with the HD 6990 in some of our new benchmarks including H.A.W.X 2, Lost Planet 2 and DiRT 2, however, when we were testing the performance of Dragon Age II the HD 6990 died on us. At the time of it's demise the card was set at the stock 830MHz setting and the BIOS switch was in the default position. The fact that it died could have been that we tested the graphics card at both the 375W and 450W settings, but since the review we have left the settings at default level.

After our HD 6990 failed AMD contacted us to see if they could get a look at our graphics card and see if they could isolate the issue. We shipped are graphics card to them in the first week of April and a few days later we got our response to what happened. Apparently, during testing one of the solder points on the graphics card broke loose, due to rapid cooling and heating, which resulted in the card not being able to function. This is actually the best case scenario, as it is not indicative of a problem with the Antilles GPU or the overall board design, but rather just an issue with some pre-production models. This means that the cards currently circulating on the market should not have the same issue as our review sample.

Also, AMD was nice enough to send us a new HD 6990 to use for future testing, which should arrive at the Neo labs soon. A big thanks to AMD for letting us know why our card malfunctioned and for getting us a new one!