ATI released a new revision of the X1900GT, something they have done for a lot of past cards as well.  In this particular case, they lowered the core speed, while raising the memory’s.  Legion Hardware puts the 2 cards head to head, and shows what you can expect to see because of this change.
“Well there you have it, the second revision of the X1900GT is in fact slower than the original. ATI did make an effort to cover up the weaker core of this second revision, which they did by using faster memory. However, the 63MHz slower core was not properly compensated for by the 120MHz faster memory, which resulted in any where from a 3~9% performance loss at 1600×1200. Some of you probably might not think much of this and while it’s not the end of the world, it is more the principal of the thing.”

Here are some more Graphics Card articles from around the web:

Click Here to go to Video Cards   Graphics Cards