A 14-Way Comparison Of NVIDIA vs. Nouveau Drivers
Next, the various sensors were recorded while running the Lightsmark test profile on the Phoronix Test Suite. With this OpenGL workload, the Phoronix Test Suite also logged the CPU usage. Similar to some earlier Phoronix results, the CPU usage when using the Nouveau driver was actually lower than the binary blob. In some cases, the CPU usage for this AMD FX-8150 eight-core Bulldozer processor was halved. However, the Lightsmark performance is not as nearly competitive with the Nouveau driver as the binary driver.
The GPU temperature on the passively cooled GeForce 8400GS remained much higher than the binary driver. For the other graphics cards they were usually operating at a lower temperature with the Nouveau driver, which can partially be attributed to the Nouveau driver not dynamically adjusting the fan speeds by default, so they're usually left at full-speed.