Extreme Overclocking of PowerColor R98-C3 (ATI RADEON 9800 Pro)

GPU Overclocking

Unlike NVIDIA GeForce FX 5900 Ultra GPU, the graphics processor from ATI and cards that have it don’t offer hardware monitoring capabilities or a tricky power supply circuit. Thus, they behave quite predictably during overclocking. From a certain frequency up, the screen is all littered with “lost” pixel blocks. If you don’t mind this, but keep on driving the core frequency up, the system will hang up. The ATI RADEON 9800 Pro chip on the PowerColor card worked stable up to a frequency of 540MHz. The diagram below offers you the test results for GPU overclocking while the memory frequency remained fixed:

As you see in the diagram, the card performs poorer at 560MHz GPU frequency than at 540MHz. It is just because the GPU in the PowerColor card doesn’t yet hang up at 560MHz, but already makes a jumble of the screen image. Such a work mode quite naturally doesn’t tell well on performance.

Here is the graph of the relative performance gain against the relative GPU frequency gain:

The ATI RADEON 9800 Pro graphics chip is faster during anisotropic filtering than NVIDIA GeForce FX 5900 Ultra. However, overclocking was most effective in modes with enabled anisotropic filtering, too. A higher GPU frequency isn’t much of a boost for the PowerColor card in FSAA modes.

Overall, the effect from the graphics core overclocking is comparable to the “responsiveness” of NVIDIA GeForce FX 5900 Ultra: 20% at maximum.

Graphics Memory Overclocking

PowerColor graphics card turned to have a speedier memory than MSI NBOX. The maximum memory frequency we managed to obtain and when the card worked fine was 840MHz. Below are the benchmarking results with the overclocked memory and a fixed GPU frequency:

And here is the relative performance gain:

My overclocking the graphics memory of the RADEON 9800 PRO based card was less fruitful than it was in case with the NVIDIA GeForce FX 5900 Ultra card. Most probably, ATI GPU has more than enough of memory bandwidth, even though it has eight pixel pipelines compared to four by NVIDIA chip. This is all thanks to its HyperZ III technology, which includes an efficient texture-caching algorithm as well as algorithms for work with the pixel units and Z-buffer. But again, because of this efficient HyperZ III, memory overclocking results into a smaller advantage than expected.

The highest performance gain is when full-screen anti-aliasing is enabled. The relative performance gain is then three times smaller than the relative memory frequency gain. In other cases, the performance gain lags behind the frequency growth by four times.