Power, Heat, And Efficiency
ASRock's FM2A85X Extreme6 takes a fairly big lead when it comes to energy consumption under full load, but there’s a trick behind that reading: each board attempts to cram our CPU into a specific power envelope through dynamic underclocking. The other boards would eventually idle down by around 10 W, and give up around 400 MHz while doing that. ASRock’s FM2A85X Extreme6 idled down a little faster, and we weren’t able to get its “real” full-load reading.
MSI's FM2-A85XA-G65 runs the coolest during our extended full-load test, though each board throttles down AMD's APU during the run. Disabling power management features is one way to combat this behavior. However, in the real-world, you're going to want to run with them enabled to avoid wasting power. That's why we leave them enabled throughout the benchmarks.
Using an average of averages to compare performance to power consumption, we find ASRock’s 7% power savings worth an 8% efficiency increase. Noting that the board had already began to throttle back before we could get a load reading, we estimate that the FM2A85X Extreme6 would normally place around mid-pack. This is one of those rare situations where Chris’ extended power readings (total watts required to complete the entire benchmark series) would have been more-enlightening.
We don’t have to make an estimation to understand why MSI doesn't do well in terms of efficiency, since the power consumption chart shows high idle wattage.