Hd 5870 + 5770x2

Wont work, you can only CF cards of the same series, so you can CF a 5870 with a 5850 or a 5970, but you cant crossfire any of the 5800 cards with a 5700 card and vice versa.

With current technology, I don't believe it will work. Some quck google searching lead to nothing but more forum threads without solid answers. AFAIK CF only works within the series, 58xx being a seperate series from 57xx. I imagine a 5750 will crossfire with a 5770, just as a 5850 will probably cf with a 5870. There has been some chatter about future drivers allowing more flexibility with cross-series multi-card setups, but nothing concrete about it, really.

EDIT: My google searches only revealed that chart with the top cards listed as 4xxx. Thar be proof.

Just as a note- generally it is much better to crossfire the same GPU's. 2x 5870 is better than a 5870 and a 5850, and 2x5850 is probably a better setup than a 5870 + 5850. You can end up with stuttering issues due to different rendering speeds and things like that.

Sorry, but I think you might be slightly mistaken here. Cards within the same series are built from the same chip, with shaders disabled and clocks reduced as you go down the line. This is often done in the bios (as a 4830 can famously be upmarketted with a bios flash) and thus, software can replicate the lowest common feature sets within the multicard setup. Yes a 5870 + 5870 will be better than a 5870 + 5850, but only because the 5850 gets downclocked and shaders disabled through the crossfire drivers. A 5870/50cf should in no way perform lower than a 5850/50CF, nor better, but precisely the same. I have witnessed these sort of mismatch setups a few times, and they have always performed closely to how the lowest common denominator pairing would perform.

Again, we may see an advancement in mismatched and cross-series xfire with future driver advancements, if the rumors are true, but without anything solid to go on, its just jibber jabber  

Jofa- as far as I know, it will downclock, but not disable shaders. Even so, what I was saying is there are generally more stability issues and stuttering with asymmetrical crossfire. It won't perform slower, and may perform slightly faster, but its not worth is since you are spending an extra $100+ on a 5870 compared to a 5850 for basically the performance of a second 5850, adding in some possible glitches. This comes from doing quite a bit of research into this as I was considering running a 5750 with a 5770 and included a couple of emails with an AMD rep who said performance ought to be just a little faster than 2x5750's.