Nouveau Reclocking: Buggy, But Can Boost Performance
Written by Michael Larabel in Display Drivers on 30 January 2012. Page 2 of 6. 23 Comments

After building a kernel this weekend of the "nouveau/linux-2.6" Git tree, I proceeded to run some tests. Unfortunately, it did not work as well as anticipated. For most of the GeForce 8/9 hardware tested, the re-clocking did not work. I'm currently investigating this issue with Martin Peres and hope to have some fixes and new tests out in a couple of days.

The dmesg output would reflect a change in re-clocking state, the profile level within the performance_level sysfs interface would reflect the new state, but the new values were the same as the boot state. When attempting to force the new performance level via the kernel parameter (e.g. nouveau.perflvl=3 in conjunction with nouveau.perflvl_wr=7777) the system would lock-up as shown above.

Some hardware, such as the GeForce GT 240, remains borked by Nouveau (shown above is the tiling that happens on boot with the GT 240). The only NV50-class where I experienced success was with the GeForce GT 220, where the support within Nouveau is still considered very experimental.

The GeForce GT 220 boots to a speed of 405MHz core, 810MHz shader clock, and 324MHz memory clock. When forcing the GT 220 to its highest performance state, the core is at 625MHz, shader clock at 1360MHz, and the video memory at 400MHz (or 405MHz was the value when actually applying the settings). At least for the GT 220 the settings applied, but it was not a clean experience.

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