Question about Crossfire and XFX 5850

[imExcitebike]

I bought this (http://www.newegg.com/Product/Product.aspx?Item=N82E16814150454) XFX HD5850 from MicroCenter about a month ago and I'm wanting to get another to go put in crossfire, but I'm having a hard time finding one.

My questions is:

How similar do two cards have to be to put them in crossfire?

 

[noquarter]

Crossfire is very forgiving, you can Crossfire a 5850 with any 5850 or 5870. Crossfiring it with a 5870 actually gives you the combined performance rather than downgrading the 5870 (5850+5850 < 5850+5870 < 5870+5870)