AMD is expected to challenge Nvidia's 9900 series of GPUs with the Radeon 4800 series of graphics cards, due to launch in the following couple of months. The new Radeon 4800 series will be based on AMD's RV770 graphics core, manufactured using the 55nm technology. Nvidia's G92b GPU that will power the new GeForce 9900 series of graphics cards is also built upon TSMC's advanced 55nm process.

Tomshardware Guide unveiled today the specifications of the new Radeon 4800 series.

The new RV770 GPU will reportedly have 480 stream processors, 32 Texture units, 16 ROP (same as 2900/3800), a 256-bit memory controller and native GDDR3/4/5 support. Both GDDR3 and GDDR5 memory versions of RV770 cards should be expected.

The transistor count has jumped to more than 800 million in the RV770 - expect the same amount of transistors for the Nvidia G92b.

The Radeon 4850 will debut with a GPU clocked at 650 MHz, while the shaders will be clocked at 850 MHz. The 4870 has an 850 MHz core and a 1050 MHz shader clock.

The GPU will be also equipped with a 256-bit memory controller. 4850 GDDR3 models will come with 256 MB or 512MB of GDDR3 memory, clocked at 1.14 GHz. 4850 GDDR5 versions integrate 512 MB of GDDR5 memory clocked at 1.73 GHz .

Flagship dual-GPU 4870 X2 cards will include 2048 GB of GDDR5 memory clocked at 1.73 GHz.

The 4850 256MB GDDR3 version is expected to be available fro less than $200. The 4850 512MB GDDR3 should retail for $229, the 4850 512MB GDDR5 will set you back about $249-269. The 1GB GDDR5 powered 4870 is expected to retail for about $329-349.

A dual-GPU 4870 X2 will cost you around $500.