Does crossfire require identical cards?

[Sanborn]

Hey guys, I've ran into a pickle needing to build a new computer and the R600 cards not coming out for a while (If its earlier than November then I will be happy) and have some questions.

If I buy a middle of the line ATI card right now....is it possible for me to use this card as the secondary card when the new DirectX10 cards come out. I know it wouldnt be possible to use it in DX10 games like that since the one card would only be DX9 but those wont come for quite a while.

If not.....do you think I will be able to use the substitute card for physics processing down the road ?

[jbizzler]

Crossfire on R600 will be way different than current Crossfire; closer to SLI.

They haven't said anything, but I HIGHLY doubt any current card will Crossfire with and R600. However, a mid-range card will do physics down the road just fine, regardless of the card used for graphics.