At idle, all of our Phenom IIs clock down to 800 MHz and employ similar voltage levels, so it’s no surprise to see them consume 160W each. The overclocked X4 965 Also scales back to 800 MHz, but because its voltage is manually keyed in at 1.5V, it uses significantly more power at idle.
The Core 2 Quad Q9550’s result isn’t really comparable, since we’ve been using the chip’s performance to indicate the speed of Intel’s 95W $220 CPU, and not the 65W $350 part shown here. Nevertheless, it’s interesting that Intel’s low-power part only barely beats AMD’s 130W Phenom IIs at idle. In comparison, the Core i7-920 consumes an extra 26W at idle (though to put the cost of that power into perspective, check out Don Woligroski’s analysis in How Many CPU Cores Do You Need?).
The field is separated more decisively with a full load applied to each processor (Prime95) and GPU (FurMark).
At 1.5V, the overclocked Phenom II X4 965 is the least power-friendly option—such is the price you pay for pushing these CPUs as far as possible on air. Intel’s Core i7-920 places in between the new 965 and its predecessor, the 955. Most surprising, perhaps, is the Phenom II X3 720, which uses more power than the quad-core Phenom II X4 955. And again, we see the reason Intel charges an extra $130 for its ‘S-class’ 65W chips, as the Core 2 Quad Q9550S ducks in with the lowest consumption results.