My first good Ati cards were a 2nd hand Sapphire HD3870 (PCIe) and a third hand Sapphire HD3850 (AGP). As they are made using a 55 nm process they are comparable to the nVidia Geforce GT200 series, as can my son's HD 4870 -a lucky dustbin find. My HD 4770 is even made on a 40 nm process, like the Fermi generation. Unfortunately the support for these fine cards in the latest OS-es is lacking, amongst others due to the lack of proper OpenCL support. We will miss the fine DP performance they offered.
Model/Type GPU Fab in nm Shaders TMA ROP GFLOP SP GFLOP DP TDP Gflop(SP)
/Watt
Gflop(DP)
/Watt
Radeon HD 3000 Series 1/5 of SP
Radeon HD 3850
RV670 PRO
55
320
16
16
428
86
75
5.71
1.14
Radeon HD 3870
RV670 XT
55
320
16
16
497
99
106
4.69
0.94
Radeon HD 4000 Series 1/5 of SP
Radeon HD 4770
RV740
40
640
32
16
960
192
80
12.00
2.40
Radeon HD 4870
RV770 XT
55
800
40
16
1200
240
160
7.50
1.50