Radeon HD 4870 X2: AMD presents its fastest graphics card ever

These 27 cm long dual slot cards can be had for around £315. AMD has released the Radeon HD 4870 X2, which combines two RV770 graphics chips (GPUs) on one card. This gives it double the theoretical computing performance of the Radeon HD 4870, at 2.4 trillion floating point operations per second (TFLOPS). Rival Nvidia's GeForce GTX 280 achieves 0.933 TFLOPS. The Radeon HD 4870 X2, which AMD proudly calls the "fastest graphics card in the world", has 1600 scalar shader ALUs, arranged in 16 groups of five in 10 SIMD units per graphics card. The figures for texture units and raster operations are also double those of the Radeon HD 4870 at 80 and 32, respectively. AMD improved the theoretical data transfer rate for GPU to GPU communication over the Radeon 3870 using a new PCI 2.0 bridge, which along with SidePort, boosts the rate to 21.8 GB per second – 3870 X2: 6.8 GB/s. However, as AMD explained at this year's CTO summit in Iceland, SidePort was already integrated into the hardware, but would not be activated until the launch.
AMD bumped the theoretical maximum data transfer rate between the GPUs up to 21.8 GB per second.

Like the other models in the 4800 series, the HD 4870 X2 supports Microsoft's DirectX 10.1, as well as supporting Shader Model 4.1. As with the Radeon HD 4870, AMD uses GDDR5 memory in the new card – 1 GB at 1800 MHz for each graphics chip. The two 1GB banks of memory cannot be considered as 2 GB, since the processed data for both graphics chips always has to be in the RAM. The video engine, dubbed Unified Video Decoder 2, accelerates both standard and HD video streams, and with the right software can also parallel process two HD video streams for picture-in-picture playback.

Early performance tests show the Radeon 4870 X2 delivers on its promises. Performance in benchmarks sometimes significantly outperforms Nvidia's competing GeForce GTX 280 card. In Crysis the card produces an average of 21 frames per second (fps), even at 2560 x 1600 resolution with double anti-aliasing, leaving the GeForce GTX 280 in the dust at 11 fps.

The Radeon HD 4870 X2 rounds up the 4800 series, trumping the GeForce GTX 280. Such performance has its price: the card's measured maximum power consumption is 278 watts, exceeding every graphics card tested to date in power consumption, even surpassing the GeForce GTX 280 by 22 watts.

Those not interested in paying around £315 for high performance can wait for the Radeon HD 4850 X2, which according to AMD will be launched between late August and early September. That model, based on the Radeon HD 4850, has 1GB of GDDR 3 RAM and also has 1600 shader ALUs. AMD says that the card will cost less than $400 – around £200.

(trk)