Sure, you can even do an HD4800 series with a GF8500 for PhysX (BTW, but only in XP since Vista won't allow more than one WDDM drive at this time, although there's supposedly a workaround in the works) ;
Don't know much about his conflicts, but I have a friend running it on an HD4870 with a GF8600 and he had alot of trouble setting it up (mainly just the nV drivers prefer to be loaded first), but now the only major issue is multi-monitor is pooched, regardless of whether running both from the HD4870 or from the GF8600 or one on each. Considering the immaturity of the HD4870 on Hydravision, and the equal immaturity of the physX drivers, it could be a bunch of stuff. It's funny because when running 3 monitors of the GF8600 without the nV drivers installed everything is fine, so it's obvious that yeah, it's not for everyone just yet, but it was more for him to play with it for UT3 (we both prefer UT2K4 though). Since I play UT with him and a few of our work and school friends, I told him about the NGOHQ results he wanted to try it for himself.
He's thinking of removing the GF8600 though (he usually only run 2 monitors but I brough my extra one to try surround gaming stuff too) simply because it wasn't what he was expecting from PhsyX (I think like most of us he hoped for something that no solution can really deliver yet [bullet drops, heavy interactive effects, etc]). Overall he thinks it's a wicked idea, as do I, but still just not worth the effort of driver cleanup.
Once it gets a little more wide spread and if it ever becomes the core of a major FPS title and get exploited, it's gonna make alot of people think about their setups and do this type of thing (both GTX+8600 & HD4K+8600).
oh em gee. this sounds epic if the bugs could be worked out. so this is basicaly saying (if i understand this correctly) that we can put in a 4870 for frames, and stick oh say, an nvdia card in the other pcie slot, and run the nvidia card as a physics with cuda?
u need open nvidia physx properties go to setting and enable one card for physics. does ur montior have more then 2 video ports? u need to connect 2 ports such as dvi or vga to ur graphic card so it recognizes u have 2 monitors in order to dedicate physics dont no y but its a glitch in vista using 2 connections from ur monitor kinda tricks it in thinking its another monitor. make sure sli is disabled and it should let u select a card for physics in the setting tab.