Some Good & Bad News For The Nouveau Driver
While it is unfortunate that the GeForce 9 and GeForce 6 hardware we attempted to used as part of this comparison had regressed to the point of being unstable, for the GeForce 8 hardware the performance was surprising to say the least. On the lower-end GeForce hardware, the performance of the Nouveau driver relative to the NVIDIA driver is at a surprising high point. With the GeForce 8400GS, the Nouveau driver had an average frame-rate of 13 FPS while the NVIDIA driver was just at 19 FPS, or only 46% faster. While this is still a sizable difference, the low-end GeForce Radeon HD 3650 with its proprietary driver was 3.56x faster than its Gallium3D driver.
The NVIDIA frame-rate though does appear somewhat for Nexuiz at 1024 x 768 with the 260.19.29 driver, but even with the GeForce 8600GT it was running at half the speed as the proprietary driver. With the GeForce 8500GT, the Gallium3D driver was 60% the speed of the proprietary blob. This is quite fascinating and good considering that the Nouveau driver was written via clean room reverse engineering without any support from NVIDIA.
What is a bit unfortunate though is that with the higher-end ASICs, such as the GeForce 8800GT, the Nouveau driver appears to hit a wall. With the Nouveau Gallium3D driver, the 8800GT isn't any faster than the 8600GT while the proprietary driver speeds up a great deal. For the GeForce 8800GT this leaves it at just 20% the speed of the binary blob.
When upping the Nexuiz resolution to 1920 x 1080, the Nouveau Gallium3D numbers remain rather promising for the lower-end GPUs. In fact, for the GeForce 8400GT it is running at 8 FPS with Mesa 7.10-devel + Linux 2.6.37 while with the NVIDIA 260.19.26 driver it is running at just under 10 FPS. With the GeForce 8600GT, the Gallum3D driver provides 66% the frame-rate of the proprietary driver.
Again though, when popping in the GeForce 8800GT, it's performance is being bottlenecked and locked in at the same speed as the GeForce 8600GT. The clock speeds between the 8600GT and 8800GT are similar at 540MHz core and 700MHz memory for the former and 600MHz and 700MHz for the higher-end part. The 8800GT also had 256MB GDDR3 memory while the GeForce 8600GT was equipped with 512MB GDDR3 memory. The GeForce 8800GT also had 112 stream processors versus 32 on the GeForce 8600GT and a lower shader clock (1190MHz vs. 1500MHz) and 16 vs. 56 texture units.