VTX3D Black Edition 7870 Tahiti + PCIE 3

[Greenback]

I have an Asus p8p67 deluxe that doesn't support pcie 3 so would only run this at pcie 2 speeds, which I assume would reduce the performance of this card.
So I'm wondering would I be better getting another 6870 for CF as 2 6870 out perform a normal 7870, and according to Asus pcie 3 is 36% faster over pcie 2 I'm thinking 1 of these may not even perform aswell as my 6870 in this motherboard.
I've also read that the 2500k doesn't support pcie 3 so I would need to upgrade cpu and motherboard to get the benefits out of 1 of these and that seems a little pointless with Haswell around the corner.

[Tripp]

i have it running through pcie 2 there is no slow down at all

[alienware]

Right. First and foremost. PCIE3 adds more bandwidth to the PCIE system. The problem is, nothing I've ever seen maxes out the bandwidth on PCIE2. This means that you'll see a 3% or so improvement over PCIE2 and simply because PCIE3 is slightly faster. Tom here at OC3D put it to the test when it first launched and concluded that it wasn't worth it.

Moving on...

One 7870 has 2GB of vram. One 6870 has 1GB of vram. You can add as many 6870s as you like but you can't add any more than the 1GB which is not enough any more. Battlefield 3 which is starting to get on a bit now uses way more than 1GB and when you run out it resorts to using your paging file which is on your hard drive. It's called Texture Streaming and creates horrific input lag (IE delays between you and the game).

Thus I wouldn't bother to Crossfire the 6870 as even though you'll possibly beat the 7870 in benchmarks gaming is where it counts and you will be left wanting.

Not only that but Crossfire does not work first time every time. Like SLI you will sometimes have to wait on patches and driver updates before a game will work properly with it and whilst you're waiting you will either lose performance over one card (yes you heard that right) or you will simply get single card performance. You will also get micro stutter and all of the other pains attached to running a dual GPU system.

Thus I would go with the 7870 as it's the better choice in absolutely every regard.

As for Asus' hyperbole? don't believe the hype is all I can say.

[Greenback]

Thanks that answered everything I needed to know, and considering I can sell my 6870 for £60 or so and 5 free games it's basically a free upgrade.
And as a bonus I can put my water block from the 6870 on the 7870