just did new testings with my system (amd phenom x4, 2x2gb ddr3 1600, nvidia gtx285 plus 9600gt+9600gso+matrox triple head on the gtx285)
testing with up to 7 screens @ 1024x768
about 50 fps with 1-3 layers...
with over 10 layers and effects i get under 25 fps
resolume resolution was 3072x1536
i'm very impressed from the performance... we don't get better results on a new hd6970 with 2dvi and 4 display port (and 2 tripleheads). (system was an core i7 also with ddr3 memory)
so my suggestion is the memory interface... which is 512 bit at the gtx285 vs. "only" 256bit @ ati 6970.
newer nvidia models also "just" have 384 bit interface.
and as what i've heard the memory performance is very important.
so what impressed me that the "old" gtx285 nearly outperforms the 6970 in resolume.
also interesting that nvidia seems to get better results when using more graphic cards than ati!
also interesting... the ati performed better if we set the displays down from 1024x768 to 800x600 or even 640x480. The Nvidia card didn't "minded" if the resolution was 640x480 or 1024x768 per screen!
hope my suggestions is right and would be happy from a feedback from the resolume team.