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The consolidated APU design and die-shrink gives the FM1 socket a substantial advantage when idle and on low load over AM3 when running on integrated graphics. The A8-3850/A75M-UD2H combination used 10W and 16W less when idle and playing HD video respectively compared to an X3 720 paired with a Gigabyte 890GX mainboard. These figures can also be considered on par with Sandy Bridge H67 based PCs if you factor in the power draw of an equivalent graphics card (HD 5570) to the APU's HD 6550D.
Unfortunately there was no improvement on load as the A8-3850's four central processing cores ate up 40W more than the X3 720 which is more or less what you'd expect from an Athlon II X4. Intel's energy efficiency can't be beat in this regard.
Unfortunately it is difficult to ascertain exactly how much of the energy draw is generated by the APU, as the amount of power pulled from the AUX12V connector depends on how power regulation has been implemented by the manufacturer. Though both the 890GPA-UD3H and A75M-UD2H have 4+1 power phase designs, on load the FM1 board pulled more than 80% of the total system power draw from the 4-pin AUX12V connector compared to 60~70% for the AM3 model.
To test the board's cooling, we stressed the CPU for ~15 minutes with Prime95/CPU Burn. Temperatures of the boards' chipset and VRM heatsinks (if applicable) were recorded using a spot thermometer. The highest temperatures were taken for comparison.
Given the power draw of the A8-3850 on load, the A75M-UD2H heatsink temperatures were impressively low, just 30°C and 44°C above ambient for the chipset and VRM heatsinks respectively. The 890GPA-UD3H's VRM heatsink measured 13°C higher, but this a bit misleading as it is connected to the Northbridge heatsink with a heatpipe, so it has a higher thermal burden to deal with. This illustrates one of the advantages of chip consolidation: fewer components to cool.
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