PCGH Review: Radeon HD 4870 X2

For this review a Sapphire retail card was used. We jumped at the chance to make bench all Radeon cards of the HD 4800 series with the latest beta driver to ensure comparable results. This driver is a beta version of the Catalyst 8.8 with the internal serial number 8.520.2, which has been provided by AMD.

After that we checked the new Geforce driver 177.83, which was released yesterday. Since it delivered a noticeably improved performance in Crysis, Call of Duty 4 and some other games, we decided to integrate it into the review. Unfortunately we ran out of time although we worked through the night and therefore we can deliver results for the Geforce GTX 280 and GTX 260 only.

Therefore our high-end comparison hosts the full currently available HD 4800 series and both models of the Geforce GTX 200 series.

Radeon HD 4870 X2: Powered by two GPUs

AMD puts two RV770 chips on the Radeon HD 4870 X2. They cooperate via the multi GPU technology Crossfire X. In the style of former high-end chips, AMD calls the duo R700 - the additional V stands for value and therefore mainstream products. The two GPUs communicate via a bridge chip, produced by PLX. The new chip (PEX86BB-AA50BC F) is compatible with PCI Express 2.0. This means that there are 16 lanes available to each of the GPUs, in order to prevent internal limitations.

Furthermore there is the mysterious Crossfire "Sideport”: Ati says that the graphics processors can use it to communicate with each other, but the feature is deactivated because it doesn't deliver any benefit, yet. But we don't want to raise false hope: The Sideport doesn't enable the graphics chips to access the video memory of the other chip, the data has to be stored twice. The rumors about a combined memory pool have not been confirmed.

The clock speeds match those of the HD 4870: Both GPUs run at 750 MHz and the GDDR5 VRAM, which is connected with a 256 Bit interface, at 1,800 MHz. There are 16 chips with 128 MiByte each on the board resulting in an overall VRAM capacity of 2,048 MiByte. Because of the dual GPU configuration with its AFR restriction each graphics chip can access 1,024 MiByte - twice as much as the default model of the HD 4870.

The card itself is 27 centimeters long and therefore matches the length of a GTX 280. It is crowned by an equally long cooler, which covers almost all of the PCB. This time AMD uses copper to for the GPU blocks - for the HD 3870 X2 they used aluminum. No wonder since the HD 4870 X2 has a TDP of 286 watt. While the Geforce almost matches this value (236 watt), the 160 watt power consumption of the HD 4870 looks almost decent. All in all the X2 construction weights 1,080 grams.