Questions about Crossfire X

Is it possible to run 2 3870's and a 3870X2 in quad crossfire?

Thoughts on 3x 3870's?

Have a friend building a PC right now, with the sky as the limit for budget.

2 3870s tied to a 3870x2 I doubt would work.. the 3870x2 I believe is not a dual pcb like the GX2 or the upcoming 9800

3 3870s (or 4) will work fine though.

The 3870x2 is indeed two individual RV670's with a PCI-E bridge chip built on to the card. Thus, it's effectively Crossfire-on-a-single-card for all purposes. However, because the individual cores are still part of a single larger card, I'm also assuming there's only one BIOS.

So it's entirely possible (and in my opinion, quite likely) that you will not be able to bridge a standard 3870 card to a seperate 3870x2 card. I guess it just depends on how ATI allows it to work...

Also, I haven't heard anything about using a 2nd or 3rd card for physics. Was that ever implemented, does it work? Anyone have any information on it?

I'm still running an old 939 system with dual X850's is there any chance my old RD580 chipset will support 2 3870 X2's in crossfire or will I have to upgrade everything to crossfire X

My mobo is an Abit AT8 32X

Its Tax refund time and definitely time to upgrade. I heard about a 3870x2 with support for 4 monitors I'd love to be able to run 8 monitors at once I have 3 and a TV right now. I also like that the 3870 doesn't require you to disable monitors when you enter crossfire mode. So Ive heard .. any one know if the RD580 will support these cards in crossfire?

AFAIK, any non-NV chipset with 2 PCIe 16x slots (electrical) will support Crossfire. All of the circuitry is on the cards themselves.