Retesting the Radeon HD 4830: Too Few SIMDs Enabled

Performance Improvement with 8 SIMDs

The maximum theoretical performance difference between the two configurations is 14.3%. We re-ran our tests at 1680x1050 for all games but Crysis and Age of Conan which we re-ran at 1280x1024. We computed the percent increase between our previous data and the new numbers and plotted them on the following chart. To get a better sense of the significance of the performance increase, we set the maximum on the x-axis to 15 (to reflect the maximum performance increase we could possibly see).

We did re-run all of our numbers, but rather than reporting them all here, we have just updated our previous article with the corrected data. This shows that there was indeed an impact, but that it wasn't quite as large as the theoretical maximum. Because the only difference between this and the 4850 is clock speed an the number of SIMDs, this would indicate that there while more compute and texture hardware does improve performance, the performance of AMD hardware doesn't scale linearly with SPs. NVIDIA hardware does come closer to scaling linearly with SPs as we've seen in past tests (and as evidenced by the GTX 260 core 216), but the architecture is a bit different. It is possible that the bottleneck in the games we tested is just elsewhere and we would see more linear scaling on more shader intensive code.

In any case, while the increases are significant (in most cases), the impact on our conclusions isn't huge. It doesn't fundamentally change the class of the hardware.