Is it possible to use Nvidia cards with SLI alongside AMD Radeon cards with crossfire?

Question

A total of 4 PCI-E cards. 2 with Crossfire and 2 with SLI. I know Nvidia disables Physx if it detects AMD cards, but let's assume we'll not use Physx anyway. Also under the assumption that we have a 4 PCI-E slot motherboard.

Answer 1

Is it possible to use Nvidia cards with SLI alongside AMD Radeon cards with crossfire?

Since Vista windows supports multiple graphics drivers. That means that you can mix cards from different vendors. E.g. one Matrox card and one AMD card, or one AMD card and one Nvidia card.

Now that answers the first technical asked part (no Crossfire or SLI used, just cards capable of using that.

Now I assume that you actually want to use SLI and crossfire.

Since the AMD driver be handling the crossfire part this should just work.
Same for the Nvidia driver.

So yes, it should work.

I know Nvidia disables Physx if it detects AMD cards,

They did and later claimed this was an accident. No idea what the status is.

Also under the assumption that we have a 4 PCI-E slot motherboard.

A motherboard with 4 PCI-e slots should not be to hard to come by. (though regular office type desktops may have less).

Note that it is far more efficient to use a single fast card compared to two slower cards in crossfire or SLI. So if performance is an issue, go for the faster cards. And if a single fast card is not enough, then you probably end up with a pair (or in your case two pairs) of power hungry cards and you better have a very beefy powersupply and good cooling.

But recapping: Yes it should work.