TG Daily claims they have the specifications of the AMD Radeon 4800-series cards. The site claims the Radeon 4800 (RV770) series will be made on a 55nm process by TSMC and will have 480 stream processors, 32 texture units, 16 ROPs, 256-bit memory bus and support for GDDR3/4/5 memory.
The Radeon 4850 will debut with a GPU clocked at 650 MHz, while the shader array will be clocked 850 MHz. The 4870 has an 850 MHz core and a 1050 MHz shader clock. The fill-rate is closely tied to the GPU clock: The 4850 sports a fill-rate of 20.8 GTexel/s (32 TMU x 0.65 GHz), while the 4870 achieves a 27.2 GTexel/s (32 TMU x 0.85 GHz) performance.
The RV770 GPU is equipped with a 256-bit memory controller (512-bit for the Radeon 4870 X2: The R700 represents just two RV770 GPUs slapped together). 4850 GDDR3 models will come with 256 MB or 512MB of GDDR3 memory, clocked at 1.14 GHz (2.29 GTransfer/s), resulting in a memory bandwidth of 73.2 GB/s. 4850 GDDR5 versions integrate 512 MB of GDDR5 memory clocked at 1.73 GHz (3.46 GT/s), supporting a bandwidth of 110.5 GB/s. 4870 GDDR5 models will get 1 GB of memory clocked at 1.94 GHz (3.87 GT/s), achieving a maximum bandwidth of 123.8 GB/s.
Flagship dual-GPU 4870 X2 cards will include 2048 MB of GDDR5 memory clocked at 1.73 GHz. The Radeon HD 4870 X2 will be introduced at a later date (and could see spec revisions).
Here's a quick overview:
Radeon 4850: 650MHz GPU, 850MHz shaders, 256-bit memory bus, 256MB or 512MB GDDR3 clocked at 1140MHz or 512MB GDDR5 clocked at 1730MHz, 110W TDP (sub-100W for the 256MB GDDR3 version), single-slot cooling. Prices: 4850 256MB GDDR sub-$200, 4850 512MB GDDR3 $229 and 4850 512MB GDDR5 $249-269.