5770 x2 and 128 bit?

[Zilliak]

I have a gigabyte motherboard the ud3h 785g. And it has x16 lane and a x4 lane. Both are pci e 2.0 What i don't understand is if i have two 5770 and i want to run them in crossfire what will be my performance gain and it will mean that the memory will increase from 128 to 256. Please, someone enlighten me. Or should i get a 5850.

Heres the link to my motherboard for those who can explain to me what i should do.

http://www.gigabyte.us/Support/Motherboard/Manual_Model.aspx?ProductID=3140&ver=#anchor_os

 

[Ritwik7]

Using 2x HD 5770 will give you a performance boost over a single HD 5850. However, your memory bandwidth will remain 128 Bit as far as I know. That should not affect your gaming performance as the HD 5770 scales well in CF.

That being said you might want to go for a single HD 5850 now and once prices do drop slightly add a second one in CF.