Doom 3 on my 5900-based system

[Harlock]

Ok, bottom line. Doom 3 runs horribly slow on my system, and I can't figure out why.

Athlon XP 2500+, OC'ed to PR3000-ish
NVidia 5900FX 128 MB, OC'ed to 450/950, latest drivers
1 Gig of twinmos RAM (dual channel, 512 per bank, dual ch on in bios)
Asus nforce2 MB, latest drivers (189 bus speed)
using on board audio
installed/played on striped 160GB SATA drives, defragged


I can only play this game at 640x480, high quality. 800x600 isn't playable at all.

Symptom:
When you view certain geometry (certain scenes), the framerate drops to <10 fps. If I stare at the floor, I get over 30fps.

Video drivers are set to highest performance, d3d settings are all 'application controled'.

I am shutting down all non-critical processes before playing.

Any ideas why other people with the same setup as mine are getting 2-3 times the performance from this game??

 

[^eMpTy^]

try clocking your card back to stock speeds...