In mid June, AMD will launch another new series of graphics cards. These new series HD 4800 series will have more muscle to challenge the NVIDIA GeForce cards. It is said that the HD 4850 is 20% faster than the 8800GT and HD 4870 is 20% faster than the 9800GTX.
As we all know, GeForce 9800GTX is only 10% faster than the 8800GT. We are able to get a clearer picture of the performance of these 4 cards as shown in the diagram below. In 3DMARK06, Radeon HD 4870 will be 32% faster than 8800GT, 22% faster than 9800GTX and 12% faster than 4850.
AS for 4850, it will be 20% faster than 8800GT and 10% faster than the 9800GTX. (~source)
AMD Radeon 4850 and 4870 3DMark06 Benchmarked
AMD Radeon 4850 and 4870 3DMark06 Benchmarked 
