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8. AMD’s High-Performance Graphics Update Not Expected to Radically Boost Performance – Sources

For months numerous web-sites have been claiming that ATI, graphics business unit of Advanced Micro Devices, planned to release a major update for the Radeon HD 4800-series family. The code-named ATI RV790 was supposed to feature higher number of shader processors and performance considerably higher compared to the Radeon HD 4870 graphics card. Well, despite of rumours floating around the Internet, sources familiar with the RV790 said in mid-February that ATI’s approaching update for the high-performance graphics segment would not bring in considerable performance improvements as the new product would just feature improved clock-speeds over existing graphics boards. 


ATI Radeon HD 4890 graphics card

Just like its predecessor, ATI RV790 graphics processing unit features 800 stream processors, 40 texture units, 16 render back ends as well as 256-bit memory bus compatible with GDDR3, GDDR4 and GDDR5 memory types. The RV790 features 850MHz clock-speed, but add-in-card manufacturers may clock the new chips at speeds up to 1000MHz. ATI recommends its partners to clock 1GB of GDDR5 memory to 3900MHz. While the RV790 chip resembles specifications of the RV770 and the chip is still made using 55nm general purpose process technology, the novelty is not hand-picked RV770 with high clock-speed potential, but a reworked graphics processor. In fact, the RV790 even has higher transistor count: it features 959 million transistors, 3 million higher compared to RV770. 


ATI Radeon HD 4890/RV790 scheme

In order to enable considerably higher clock-speeds of the RV790, ATI had to reconfigure the chip: to re-do the power distribution of the ASIC, re-time it and also add larger de-coupling capacitors on the ASIC to clean up noise and increase signal integrity (this latter element is the primary cause of the increased transistor count). 

It was not logical to expect the RV790 to be an enhanced version of the RV770 in terms of the number of stream processors or other elements. The recent history of graphics processing units does not know examples when a company introduced a brand-new GPU with new internal design that would only be 20% - 30% faster compared to predecessor in the same price-range. Moreover, it would not make much sense to unveil a considerably faster graphics chip several months before the release of the DirectX 11-compatible GPUs. Finally, considering current 40nm yields at TSMC's fab, it would hardly make much sense to start transition to 40nm process technology from a relatively big chip, at the same time, it would not make much sense for ATI to make the "enhanced" RV790 using 55nm fabrication process.

 
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