AMD Radeon HD 6990 Review - PAGE 3

The visually the HD 6990 is consistent with the other graphics products in the Northern Islands series. This consists of a black heatsink shroud that has red accents along the sides. Where the HD 6990 distinguishes itself from the others though is the central blower sytle fan as well as the overall dimensions. To this point the largest Northern Islands graphics cards have been the HD 6970 and HD 6950, but to pack in dual cores and 4GB of memory on a single PCB the length had to be extended to 12 inches. This gives it a rather large footprint, but the dimensions are still roughly the same as the HD 5970.

Each GPU in the HD 6990 utilizes the full potential of the 40nm Cayman architecture, but with two available cores the specifications are essentially doubled. This gives the AMD HD 6990 a total of 3072 ALUs, 64 ROPS and 192 texture units, which with the 830MHz clock speed gives the board a total compute power of 5.1 TFLOPs. Additionally, it comes with a 4GB frame buffer (2GB per GPU) of GDDR5 memory that is rated at 1250MHz (5.0Gbps QDR) and runs on a 256x2-bit memory bus. This gives the HD 6990 substantial amount of compute power along with a large frame buffer.

With the "AUSUM" dual BIOS feature the HD 6990 essentially has both a stock and overclocked setting that can be applied via the BIOS toggle. When using the overclocked BIOS setting the HD 6990 maintains the same internal specifications and memory speed, but the GPU clock speed is increased from 830MHz to 880MHz, giving it a compute power of 5.4 TFLOPs. In addition the GPU speed the voltage level is also increased from 1.12V to1.175V, which gives the HD 6990 a total Power Tune rating of 450W. This increases the overall performance and the additional power could also yield higher overclocks.

The HD 6990 will ship with the BIOS switch in the in the default 2 position and there will be a yellow warning sticker covering the "AUSUM" 1 position. The additional power and clocks speeds will increase the cards performance, but with each card will have a warranty sticker over the switch, which effectively voids the warranty if the option is used. It is very disappointing that AMD will not cover the warranty when the "AUSUM" switch is used, and strange that they would include it as an option if its not going to be covered.

The AMD HD 6990 has a single CrossFire bridge connector, which will allow for 2-way QuadFire support. The power consumption for dual Antilles graphics cards would be astronomical, but AMD has improved their CrossFire scaling with the 6000 series and state that in a 30" display configuration we should see scaling upward of 1.8x or higher.

The AMD HD 6900 series graphics cards utilize a PCIe x16 2.0 Bus type. This standard has a larger bandwidth than previous versions and is backwards compatible, so there will be no issues when using the HD 6990 with a older PCIe interface.

The power connectors are found toward the rear of the PCB and face outward at a 90° angle. In all there are two 8-pin PCI PEG connectors that along with the PCIe bus drive the card. Through the use of Power Tune the HD 6990 will not exceed the 375W (Stock) or 450W (Unlocked) threshold.

Unlike other cards in the series the HD 6990 has an open back end to improve the airflow. With the centralized fan the air is pulled in from under the card where it is then pushed through each GPUs heatsink and exhausted out either the end. This design does mean that a portion of the hot air will be dumped into a chassis, which can increase the temperature of other internal components.

Another interesting feature of the HD 6990 is the flexible display output configuration. In all there are four Mini-DP 1.2 ports along with a single DL-DVI connector. With this configuration the board has native 5-way Eyefinity support, out of the box.

To further improve the Eyefinity support all AIB partners will include three video adapters with the HD 6990.