Energy consumptionWe used the test protocol that allows us to measure the energy consumption of the graphics card alone. We took these readings at idle on the Windows 7 desktop as well as with the screen in standby so as to observe the impact of ZeroCore Power. In load we opted for the readings in Anno 2070, at 1080p with all options pushed to maximum, as well as those in Battlefield 3, at 1080p in High:
The Radeon HD 7700s draw very little power at idle, two of them using under 10W on the Windows 7 desktop. With the screen in standby, the ZeroCore Power technology functions well and can reduce energy consumption to 1.2W!
In load, the Radeon HD 7770 draws about the same amount of power as the Radeon HD 5770 in Anno 2070 but consumes 10W less in Battlefield 3. The Radeon HD 7770s seem to be particularly well balanced for Anno 2070 with maximum details, which means that their processing and texturing units run at full speed and therefore give slightly higher performance and draw slightly more power than on average.
The Radeon HD 7750 has a significantly lower performance. Its energy consumption doesn’t vary much between the two games, which can be explained both by the different processing unit balance and PowerTune.
If we increase the PowerTune limit by 20% in Anno 2070, the reference Radeon HD 7770’s power consumption is unchanged but the reference Radeon HD 7750 increases to 48W and performance is up from 15.3 to 15.4 fps. The impact of PowerTune is therefore minimal, even if the Radeon HD 7750 seems much closer to its limit than the other cards using it. In Battlefield 3, modifying the PowerTune limit doesn’t change energy consumption for any of these cards.
Here's a graphical representation of the energy consumption readings, with fps per 100W to make the data more legible:
[ Anno 2070 1080p Max ] [ Battlefield 3 1080p High ]
Thanks to the 28nm fabrication process, the energy yield has improved significantly. Note however that each game represents a particular case and that the mid-range GeForces lag somewhat in Anno 2070 when the settings are pushed to a maximum while the architecture of the Radeon HD 7700s brings a significant gain. There’s not so much of a gap in Battlefield 3 but the trend is the same.