Penumbra overture runs slow

[janosik]

Penumbra overture runs very slow on my computer, I tried resolution 1280x1024 (all other settings default) which is not that high and the game is barely playable (not sure what the FPS is exactly).

Software:

debian unstable
kernel 2.6.18 (using in-kernel alsa)
ATI driver 8.31.5

Hardware:

Intel® Pentium® 4 CPU 2.40GHz
ATI Technologies Inc Radeon R350 [Radeon 9800 Pro]
Creative Labs SB Live! Platinum

E.g. Gish runs at what looks like normal speed, also tried Tremulous (IIRC) and it was running fine.

What does everybody else see?

TIA,

erik