Originally Posted by btarunr
It is very difficult to get a HD 4870 to run at 850/975 MHz on air-cooling. This indeed isn't just an overclocked RV770, since an RV770 can't run stable at those speeds in its existing form.
Perhaps it's a 40nm version of the same chip with higher clocks?
If Nvidia can do it, I guess ATI can too. I'm just glad they didn't go ahead and change the number to 5000.