so this provides support for the concept of RV530 and R580 being architectually close
and G71 is supposed to be clocking 750MHZ core...just for information
Now, since ATI's card will be doing more operations per pixel fill rate in raw theoretical terms means a bit less, but here is a rough idea of where these two new cards will be, compared to 7800GTX 512 and X1800XT
G71 - 750MHZ 32 TMU 16 ROP: 24,000M Texels/S and 12,000M Pixels/S
G70 - 550MHZ 24 TMU 16 ROP: 10,320M Texels/S and 8,800M Pixels/S
R520 - 625MHZ 16 TMU 16 ROP: 10,000M Texels/S and 10,000M Pixels/S
R580 - 695MHZ 16 TMU 16 ROP: 11,120M Texels/S and 11,120M Pixels/S
in raw theoretical fill rate, the G71 steps ahead by a considerable ammount (while it's pixel fill is rather close, the higher texture fillrate obviously increases performance) The next thing to note is the ATI card is planned with fairly slow memory for that high of a clock, which would lead a guess to 512-bit, or (more likely) typical ATI design with fairly low bandwidth for the GPU (if you compare R480 and NV40, R480 has a much higher theoretical fill rate in contrast to NV40, yet almost identical memory bandwidth, which does serve to lower performance)
Since the R580 can maintain more operations on the individual pixel, compared to G71, which results in somewhat higher performance than it's fill rate figures would dictate, the other thing I would guess at, is that overall 3D power from G71 and R580 will not be as large of a performance increase as NV40 was from NV38/R360, or R420 was from NV38/R360
But more along the lines of G70 from NV40/R480 and R520 from NV40/R480, it won't be a small bump but it won't be huge, and R580 adds a lot of computational power behind those pipes...