Each of the cards we tested treats power management a little differently. The following table illustrates the idle/load clock speeds observed for each board:
|Idle Clocks (GPU/Memory)||Load Clocks (GPU/Memory)|
|Radeon HD 4850||160/500||625/993|
|Radeon HD 4830||500/750||575/900|
|Radeon HD 4770||250/800||750/800|
|Radeon HD 4670||165/250||750/1100|
|GeForce GTS 250||738/1100||738/1100|
At first, it seems strange that the 640-shader Radeon HD 4830 would idle at the same power consumption as the Radeon HD 4850. However, the 4830 is being run at significantly higher idle clocks. Under load, the faster HD 4850 widens the gap and uses the most power in this comparison.
The Radeon HD 4770 scales back idle power consumption to 152W (total consumption from the wall socket), just 4W less than the 55 nm RV770 LE running 250 MHz faster. With a load applied, however, the new ATI card is 18W under the Radeon HD 4830 and 29W under Nvidia’s GeForce GTS 250. In fact, the card’s closest competitor is the mainstream Radeon HD 4670, which uses 19W less under full load.