You could always try Google...
Anyway, a quick search netted this review:
http://en.inpai.com.cn/doc/enshowcont.asp?id=6829
Seems about 5% faster than a 4850. Doesn't make much sense to me, considering how crowded ATi's upper midrange lineup already is (4850, 4870, 4870X2, 5850, etc).