- Intel i7
- AMD Radeon HD 6970
- SSD with plenty of space
- 6 GB RAM
- OpenJDK 6, 7, and Oracle Java 7 (reproducible with all three)
- AMD Catalyst 12.8 and open source driver (reproducible with both)
- Ubuntu 12.04 x86_64 and older
- Minecraft 1.3.2 vanilla and older
On this setup I am getting rubbish frame rates after a short while of playing, dropping from about 45-55 to 15 in a couple of minutes. CPU use is 40-45 even when rendering the opening screen at 1920x1280, and gameRenderer is using about 90% CPU when playing.
Rather than trying to eke out a few more FPS out of an obviously broken rendering pipeline, I really hope to find a solution to make the GPU render Minecraft.
Edit 1: Something bizarre just happened: The first thing I always change in the settings is to turn bobbing off. Turns out that re-enabling bobbing makes the frame rate shoot right back up from 15-20 to 30-50 (mostly around 30) in fullscreen mode! It is still rather erratic, bumping down to 15-20 sometimes, but usually only for a few seconds. Also, the debug mode (F3) shows that 100% of the time is spent in "unspecified".
Edit 2: That seems to have been a dud - I disabled bobbing again a few minutes later, and it's been running at 20-40 FPS since. The snooper reports 24 FPS.