1). Are the XFX HD 5850 and XFX HD 5850 Black Edition compatible. I read in the static thread that the two cards had to have the same memory and the same clock.
If they aren't, then that sucks, as I have already bough the new card and figured since they were same model, essentially, that I was good. However, I am sure that I can "underclock" the BE and waste the $30 extra that was spent.
Looking at the attached picture, these cards are WAY too close. I have two other PCI-E 2.0 slots but they are at x8 and x4. I want to spread the apart as the fan on the upper card is directly on the back of the lower card. With the air coming in at that point, it is very constricted.
2). If I move the bottom card to the next slot down, do I lose any abilities or "awesomeness" due to the x8 or x4 deal? And if I do, is it okay to leave them as is?
1_Yes they are compatible and you don't need to underclock any of them, both will operate at their default speed http://www.tomshardware.com/forum/245454-33-crossfire-f...
"What about brands ?
Well the brand doesn't matter , again for example , you can use a XFX card with a EVGA card , or a SAPPHIRE card with a DIAMOND card , just make sure they have the same memory and same clocks.
What happens if the cards have different amount of memory?
For ATI cards;
One of the cards will raise/lower its clock speeds to reach the other card's speeds.
For Nvidia cards;
Well it "was" like ATI with older drivers, but with new drivers its quite different.If you use 2(or more) Nvidia cards with different clock speeds in SLI mode,none of them will change their clocks and they will perform at their default clock speed."
2_x8 vs x4 won't make much of a difference in "CrossFire" mode(for PCI-e 2.0 cards), however if you use only one card,then there is a significant difference between x8 and x4