AMD Radeon HD 6990 Video Card Review

The AMD Radeon HD 6990 (Cont’d)

The Radeon HD 6990 comes with two ROM chips, selectable through a switch located near the CrossFireX connector, see Figure 5. The card comes with this switch on the position “2,” which loads the default clocks and voltages of the video card (830 MHz, 1.12 V). When moved to the position “1,” the video card is overclocked to 880 MHz and voltage is increased to 1.175 V. We will test this card with its switch in both positions.

Figure 5: Dual-BIOS switch

In Figure 6, you can see the video card with its cooler removed.

Figure 6: Video card with the cooler removed

Figure 7: Voltage regulator

The GPU cooler can be seen in Figure 8. It uses two separate heatsinks, one for each GPU. The heatsinks use vapor chamber technology, which is a technology similar to the one used on heatpipes. According to the manufacturer, this GPU cooler can dissipate up to 450 W.

Figure 8: The GPU cooler

Each GPU is connected to eight 2 Gbit GDDR5 chips, for a total of 2 GB per GPU (2 Gbit x 8 = 2 GB) or 4 GB total. Each chip is connected to the GPU using a 32-bit data lane, making the video card’s 256-bit memory interface (32 bits x 8 = 256) per GPU.

The chips used are H5GQ2H24MFR-T2C parts from Hynix, which support up to 1.25 GHz (5 GHz QDR) and since on this video card memory is accessed at 1.25 GHz (5 GHz QDR), there is no margin for you to increase the memory clock rate while keeping the chips inside the maximum they support. Of course you can always try to overclock the memory chips above their specs.

Figure 9: Memory chips

Before seeing the performance results, let’s recap the main features of this video card.