well i talked my fiancee into it i just ordered a 2nd 4870 but it wont be at the store till monday im thinking of just giving it back and getting a 4870x2 my question is i already own a 4870 can i still crossfire a 4870 and a 4870x2 if i order a 4870x2
OK, 650W is too little for HD 4870x2 + HD 4870. Reviewers for the HD 4870X2 recommend 700W for a system with HD 4870X2 alone. At a minimum I'd recommend Antec TPQ-850 or Toughpower 850W. Also, CoolerMaster PSUs are not among the best.
To the guys who say HD 4870X2+HD 4870 works: do you know this for a fact, or are you just assuming it will work because it's logical and desirable? There's a difference, you know... For example HD 4870+HD 4850 works, but HD 4870+HD 3870 doesn't, and AMD has confirmed it never will.
One more thing: HD 4870X2+HD 4870 means 3 GPUs. Windows XP drivers will be limited to 2 GPUs, AFAIK. That is, if HD 4870X2+HD 4870 works, you will need Vista to make it work. Also, considering the amount of video RAM involved, you should have a Vista 64-bit version. With a 32-bit version, the memory space left for addressing system RAM will be way too small and performance will be hurt.
anything thats in the same seies will work a 4870 and a 4850 can be cf cause there both 4800 series graphics cards a 4870x2 and a 4870 should be able to be crossfired since there still both 4800 series cards.