Techpowerup found some details regarding the specifications of ATI's upcoming mainstream RV740 and high-end RV790.
The RV740, a mainstream GPU from AMD, is on course of becoming the first GPU in production, to be built on the 40nm manufacturing node. It carries 640 stream processors and a core clock speed of 700 MHz. It features a 128-bit wide GDDR5 memory bus, churning out bandwidth that rivals equally clocked GDDR3 with double the bus width. The memory bus will be clocked at speeds between 800 and 900 MHz (3.2 GT/s and 3.6 GT/s). Products will carry 512 to 1024 MB of memory. The GPU houses 32 texture memory units (TMUs) and 8 raster operations pipelines (ROPs).
As for the RV790, surprise: it shares the same clock speeds as the RV770XT: 750 MHz (core) and 900 MHz (memory). The samples were equipped with 1 GB of GDDR5 memory with chips made by Qimonda. The memory bus width remains unchanged at 256-bit. With so much similarity with the RV770, the shader domain is all that remains to serve as the differentiation factor, apart from the newer manufacturing process that hypothetically facilitates larger overclocking headroom.