nVidia 8800 Ultra Bottleneck Investigation
Introduction
With so many new GPUs coming out from nVidia lately and benchmark figures flying around everywhere, I thought it would be interesting to examine where the performance differences might be coming from. The test is quite simple: since G80 (and newer) nVidia hardware have separate core, shader and memory clocks, I simply underclocked each individually the same percentage to see which has the biggest impact on performance.
Note that the shader clock can be adjusted individually, but there’s a limit how far it can go from the core. In the case of my 8800 Ultra, the most I could go down from 1512 MHz was 1224 MHz, or a 19% drop.
This 19% figure will form the basis of all my underclocking; I’ll run everything at stock and then underclock one component at a time to see which causes the biggest difference.
Hardware
- Intel Core 2 Duo E6850 (reference 3.0 GHz clock, 1333 MHz FSB).
- Gigabyte GA-G33M-DS2R motherboard (Intel G33 chipset, F6 BIOS).
- Single 8800 Ultra (768 MB, clocks as specified).
- 4 GB DDR2-800 RAM (4 x 1 GB, dual-channel).
- X-Fi XtremeMusic.
Software
- Forceware 169.21, high quality, optimizations off, LOD clamp, 16xAF and AA (as indicated) forced.
- Highest quality 2.1 sound.
- Windows XP Pro 32 bit (SP2, DirectX March 2008).
