Would I need a new motherboard to get the best out of CrossFireX?

[King Mustard]

I have an Asrock H77M, and it "Supports AMD Quad CrossFireX™ and CrossFireX™".

However, since it only contains 1x PCI Express 3.0 x16 slot, I'm guessing putting a second card into the next fastest slot (the PCI Express 2.0 x16 slot) will limit the overall performance?

I guess what I'm asking is:

Do I need 2x PCI Express 3.0 x16 slots to get the best out of 2x 7870 Tahiti LE video cards?

 

[chernobog]

Doubtful it will have much impact, PCI-E 2.0 will suffice.

If you had 2 7970's then that would be a different story.

Mixing them together won't cause problems.

If you have problems with Crossfire then get Radeon Pro and tweak profiles for games, the fix is coming by end of July.

 

[King Mustard]

Doubtful it will have much impact, PCI-E 2.0 will suffice.

If you had 2 7970's then that would be a different story.

Mixing them together won't cause problems.

If you have problems with Crossfire then get Radeon Pro and tweak profiles for games, the fix is coming by end of July.

Ah, thank you

Below is the port layout of my motherboard.

My 7870 Tahiti LE is currently in the top slot (and it annoyingly covers the top PCI slot).

Where would I plug the second card - in the bottom slot?

How do they then connect to each other if they're so far away? (I'm new to CFX/SLI)