Let’s have a look at the general specifications of the Radeon 4800 series, which is based on the RV770 graphics processor. The new GPU has 480 stream processors or shader units (96+384), 32 Texture units (up from 16), 16 ROP (same as 2900/3800), a 256-bit memory controller and native GDDR3/4/5 support (expect GDDR3 and GDDR5 memory versions of RV770 cards).
The transistor count has jumped from 666 million in the RV670 to more than 800 million transistors in the RV770.
The manufacturing process has been carried over: TSMC is producing the GPUs in 55 nm (the process itself is called 55GC).
The Radeon 3800 series had a serious flaw called texture low fill-rate, which was addressed by ATI with an increased number of TMUs (Texture Memory Unit) from 16 to 32. The specifications indicate that 16 TMUs can address 80 textures on the fly, which means that 32 units should be able to fetch 160 in the RV770: This should allow the new GPU to catch up with NVIDIA’s G92 design. However, the G92 has 64 TMUs that were enabled gradually (some SKUs shipped with 56), resulting in a fill-rate performance that beat the original 8800GTX and Ultra models.
ATI’s RV770 will be rated at a fill rate of 20.8-27.2 GTexel/s (excluding X2 version), which is on the lower end of the GeForce 9 series (9600 GT: 20.8; 9800 GTX: 43.2 9800 GX2: 76.8).
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