Shaders haven't doubled and I didn't imply they did; but with increasing clock rates, math processing power has doubled. Z-fill per clock has either doubled or quintupled, I'm not sure; and as gojdo pointed out, the main bottleneck for R600-based cards, texture management rate, has nearly tripled (although I'm not sure on the clock rate, for the core except shaders is it really %35? I thought it was just 800 or 900MHz); and counting double the memory bandwidth and memory amount, nearly everything you can imagine has at least doubled.

The performance has to be somewhere close to double 3870. If it's only 1.5x, HD4850's price of $220 doesn't make any sense at all against the $150 HD3870. To me, everything points to the direction that 4870 will at least be 1.7 or 1.8 times HD3870, and 4850 will be at least 1.4-1.5 times HD3870, which fits in the 3dmark Vantage performance scores we have heard (4850 being slightly faster than 9800GTX)