We've repeatedly stated that AMD would offer high-end CrossFire multi-GPU solutions. In fact, AMD has a single GPU competitor only to oppose NVIDIA GeForce GTX 260, the cheapest card in the series. We're talking about Radeon HD 4870, the fastest single GPU solution of the Radeon HD 4800 series. The company itself mentioned on many occasions that it was going to manufacture single GPU graphics cards for mid-end and lower high-end segments, and offer dual-GPU solutions for the top segment. First of all, it was planned to oppose GeForce GTX 280 with CrossFire configurations based on two separate Radeon HD 4850 or Radeon HD 4870 graphics cards. - Digit-Life

ATI Radeon HD 4870 X2 2GB Dual-GPU Board Review

The Radeon HD 4870 X2 card is based on two RV770 GPU's, connected with a special bridge, uses CrossFire technology and alternate frame rendering. The theoretical part about the dual-GPU card based on the known architecture cannot be long, it's just two RV770 GPU's installed on a single PCB with memory, bridge and other steering elements. And this dual-GPU system is based on CrossFire, implemented on the hardware level, PCI Express lanes and the bridge are installed right on the board. There is a little difference from a system based on two Radeon HD 4870 cards solely because of some architectural changes.

Using the 55nm fabrication process for not very complex GPU's allows to produce dual-GPU solutions of such power. AMD even didn't have to reduce clock rates as it had happened in the past. Moreover, the company installed more memory on both modifications. By the way, these cards bear expected names, as the X2 stands for a double kit of GPU's and video memory since the Radeon HD 3870 X2. Besides, along with the top Radeon HD 4870 X2 card with two gigabytes of GDDR5 memory, the company plans to launch the Radeon HD 4850 X2 with two gigabytes of less expensive GDDR3 memory in the future.

The concept of this design has apparently migrated from the Radeon HD 3870 X2. The only changes have to do with GDDR5 memory peculiarities and higher power circuit requirements. The card is equipped with a new bridge from PLX technologies to set up internal CrossFire mode between the GPU's. The cooling system is exactly as in the Radeon HD 3870 X2 card. Only the heatsinks have been changed. The operation principle is the same, a turbine drives air through the heat sink. There is a big advantage as the hot air is blown out of enclosure and does not stay inside. There are some drawbacks as well of course.

Out of doubt, this product can be theoretically twice as fast as the Radeon HD 4870 card. But in practice, it's less fast. So maturity and performance of a given game depends solely on how well programmers finetuned the corresponding driver. There are a lot of games, where all these super powerful dual-GPU cards demonstrate low performance and lags, to make things worse. It happens, when a processor has finished its previous task and gets an easy assignment, while the second processor is loaded to the brims, so overall performance slumps. Visually, it will look as irritating lags.

It's really a pity that AMD just stopped producing some high-end single GPU solutions comparable to similar products from NVIDIA. Now it only makes mid-end single-GPU cards, pairing them for the high-end segment. Drawing a preliminary bottom line, we can state that R700 is actually very fast and, despite potential drawbacks, it seriously threatens top solutions from NVIDIA. We have already seen the Californian company cutting prices for their GeForce GTX 200 series.