Yes I already tagged this 'new' topic as solved, but I thought it might be worth sharing, what I just found out.
So I installed my system new and fresh and hip. (Arch Linux 64bit, if anyone is interested, more precise Antergos, because I am lazy)
Eager to pwn some random idiots... uhm noobs, I was very disappointed, when I noticed that running Sauerbraten gave me around 20 fps.
So I reinstalled the driver, threw the old xorg.conf away and did the usual. Nothing worked.
I noticed that, Sauerbraten used the mesa OpenGL driver, which isn't really bad, except, that in this case it turns out to be the source of the low fps problems. Therefore the solution was:
[SOLUTION]:
- remove mesa-libgl
- install nvidia-libgl
Starting sauerbraten revealed the correct driver is being used, and....
tadaa! the beast is unleashed: 900-1100 fps.
If you've found out technical related solutions or want to share your knowledge, let us know!