ATI HD 4890 is overclocked HD 4870 After All?
 

The 4890 is not a new ASIC, it may or may not be a new stepping of the R770, but it is not a new part. It is not 40nm either. On top of that, there is no R790 in the works at all. The new board is called the 4890, and it is simply a much higher clocked 4870.

It will be at least 20 per cent faster than the 4870, a real kick in the pants, but will take a bit more power. The added power will require five-phase voltage regulation, so there will be a new board layout, quite likely lining up with a new downcosted 4870 board as well.

http://www.theinquirer.net/inquirer/.../ati-4890-asic

Sadly, if this is true, it doesn't come to much of a surprise.