[quote][quote]and what if i install 2 hd5970 in crossfire and 1 gtx 480 for physx?
Can i play game with good frames and physx?
and can i watch videos in 3d if i have nvidia 3d vision?[/quote]
You can. More importantly: Would you want to? No.
You have to remember that all a GPU really does is render little squares of color called pixels on your screen. Whatever math it has to do with shader calculations, texture resizing or whatever, the END PRODUCT (i.e. the bit that comes out at the end or the bit that really matters) is how fast it can draw and output these little squares of color. That's why you have to use two of the same cards when you crossfire or SLI - two different cards at different clocks would cause the screen to be out of sync, and your computer would really start to freak out as a result.
Crossfire/SLI basically makes it so that one card renders half of the screen, and another card renders the other half - it doesn't magically double computing power or memory, it simply halves the workload of one card (yes, there is a difference).
You could do this (have the crossfired 5970s render your game and use the 480 for physx), although using a gtx 480 JUST for physx is a complete waste.
Remember PHYSX IS NOT the same as PHYSICS. You have to be playing a game with physx support (imho the only ones worth playing right now that I can think of are UT3 and Mirror's Edge). If you wanted to watch videos in 3d or play games in 3d, you would have to connect your 3d-capable display to the gtx 480 and set that graphics card as your primary device. But the downside would be that you would only be getting the performance of 1 gtx480 (if that can be called a downside at all) and your 5970s would be sitting in your case eating a lot of power and putting out a ton of heat.
So basically, if you have enough money to blow on 2 5970s and 2 gtx 480s, just buy 2 480s, put them in SLI and spend the rest of your money on some good ram, a SCREAMING processor (because yes, unless you have a very fast processor, you will begin to bottleneck those cards), a fast hard drive, and most importantly your electric bill (because electricity makes the world co round
).
Just my 2 cents.[/quote]
Actually with regards to most crossfire systems each gpu will render one frame at a time and they will be sent out. IF it were done as you say I would foresee huge issues with synchronization between the two halves of the screen