Power consumption and efficiency
Since the A8-3800's primary distinction is its 65W power envelope, we'll begin with a look at power consumption. There's a lot going on in the graphs below, I'll admit. Most of the systems are configured as similarly as possible, with the same power supply, storage, memory, and graphics card. Only the motherboards and processors vary.
However, for Llano and friends, we also wanted to take a look at power draw with only integrated graphics, so the results parenthetically marked "IGP" don't include a separate video card.
Also, a couple of the results, marked "Brick PSU", involve truly low-power configurations with only integrated graphics and a more efficient laptop-style brick power supply. We pondered putting the Llano and Core i3-2100 systems on the brick PSU, as well, but their total power draw probably wouldn't mix well with that power supply's 80W peak rating, so we stuck with our standard PSU instead. Out of necessity and because it's only fair, we did install the Core i3-2100 in a smaller microATX motherboard, the Intel DH67BL, for the IGP power tests.
We'll start by looking at the raw power draw results, and then we'll parse them in various ways.
The A8-3800 system's power draw at idle is comparable to the Core i3-2100's, overall. However, at peak, the Core i3-2100 rig draws substantially less power, even though the two chips ostensibly share the same max power (TDP) rating. The gap is largest without a discrete graphics card in the mix, where the A8-3800 setup pulls over 20W more than the Core i3-2100. That gap shrinks when we involve a discrete GeForce and shift the Core i3-2100 to a larger motherboard.
Still, the contrast between the A8-3850 and the A8-3800 is considerable. Our A8-3800-based system requires about 30 fewer watts, either with our without a discrete GPU.
If we concentrate on the period when each CPU is processing the rendering task, we can get a nice measure of power-efficient performance. When we do that, the A8-3800 isn't especially impressive—more efficient than the A8-3850, but less so than the Core i3-2100.