Here's the power supply's total consumption, which sums up the consumption of the configuration as a whole as well as the Tagan U15 530 W power supply losses, which are 20% on the range of power considered here.

It's not really surprising, the HD 3800 brings about a huge drop in consumption compared to the HD 2900 XT, but the extent of it surprises us; the drop in peak total consumption amounts to 109 W when going from a 2900 XT to the 3870 with performances that are slightly superior! The 55 nm process does its share but, unfortunately, doesn't enable the HD 3800 to go lower than the 8800 GT in high performance (despite a maximal consumption announced at 105 W for the HD 3870, as did NVIDIA, and 95 W for its 3850). AMD maintains its technological lead, but despite all this the performance-consumption ratio remains in favor of NVIDIA, which is quite disappointing for AMD.

Let it be noted however that the advantage that comes from using a smaller process is blatant in idle consumption, which may be the most important in the end, for your electricity bill and energy waste and a new record was achieved by the HD 3850, the 3870 proving to be on par with the 8600 GTS. In the end, it's much better for AMD which comes back to a reasonable level of consumption, but nevertheless not as good as NVIDIA in peak.