The Athlon At 800 MHz
Kryotech's system offered us a look at the performance of an Athlon at 800 MHz. Due to Athlon's half-speed 512 kB L2-cache and its big dual 64 kB L1-caches we expect that Athlon scales with clock speed very well. Let's have a look at the results.
3D Studio Max scales perfectly, we see an increase of the 33% that 800 MHz is more than 600 MHz. The rendering process is running almost completely within Athlon's big 1st level cache. Half-Life requires a lot of CPU-performance too, which is why it benefits from the 200 MHz higher clock frequency by 24%. Sysmark 98 under Windows98 and NT is restricted by the hard drive performance, which impacts the performance increase down to 20 or 19%. Quake2 and Quake3 are depending on the graphics card performance, even at a resolution of only 640x480x16. This is why the performance increase at Quake3-Test is only a meager 12%.
Overall we should still expect an average performance increase of 60-90% of the clock speed increase with AMD's new Athlon. The big caches will make sure that this doesn't change even at clock speeds beyond 1 GHz.
We would like to take the opportunity and mention one little issue with Athlon's L2-cache that could easily be forgotten. Running the Athlon at 800 MHz doesn't ask too much from the Athlon-core-chip, but it requires the L2-cache to run at 400 MHz. Whilst AMD is producing the Athlon-core, it doesn't have quite as much control over the production of the L2-cache chips. At this point in time it's very hard to find L2-cache chips that actually run stable at 400 MHz and it will be even more difficult to find faster chips. The solution for this situation would either be an on-die cache in future .18µ Athlons or external cache-modules produced by AMD, just as Intel is manufacturing the external L2-cache of the Xeon-CPUs. There's of course a third possibility as well, but it's the least attractive one. AMD could start running the L2-caches of faster Athlons at only one third of the core clock, but this will cost performance.