Power Consumption And Efficiency
We now know that, as a host processor, Core i7-3770K really isn’t that much faster than Core i7-2700K. But we also know that Ivy Bridge should be capable of delivering better (or at least similar) performance in a significantly lower thermal envelope. In this case, the -3770K is a 77 W part, whereas Core i7-2700K is a 95 W processor and the Sandy Bridge-E-based chips are rated for 130 W.
Rather than simply letting each chip sit on the Windows desktop and then spin them all up, reporting idle and load consumption figures, we instead created a script using all of the tests in our benchmark suite (aside from the games and the Google Chrome compilation) with short rests in between. The resulting metric is more than an hour long on even the fastest processor in our collection, and it’s truly a real-world mix of idle and load.
It’s frankly pretty difficult to make sense of the raw, logged data, even with our normal chart expanded out to make the hour-plus run more readable. Certain segments make it quite clear, however, that the Core i7-3770K is the lowest-power contender tested, followed by the Core i7-2700K, the Core i7-3930K, the Phenom II X6 1100T, and finally AMD’s FX-8150. What about the -3960X? We have the data for that one as well, but the additional line makes this chart even more of a mess, so I left it off. I also have data for the -2550K, but I’m working on a surprise with that information.
There we go. It’s much easier to average out power consumption during each run and compare the result. As hypothesized using the line graph, we see each CPU land exactly where we expected it to, with the -3960X falling in just behind the -3930K.
It’s pretty darned easy to measure how long each sequence runs, since our logger takes a sample once every two seconds. Not surprisingly, the Core i7-3960X finishes first. It’s more interesting that the Core i7-2700K is just slightly quicker through the benchmarks than Core i7-3770K. Both AMD trail quite a ways behind.
Multiplying average power by the time required to complete the benchmark gives us total energy used in watt-hours, reflecting efficiency.
The Core i7-3770K’s solid performance, coupled with a reduction in power consumption, results in the lowest power use in the course of our suite. The Core i7-2700K follows closely behind, though.
Both of the Sandy Bridge-E chips facilitate impressive performance numbers throughout our testing, excelling particularly in threaded workloads. However, 130 W TDPs penalize the LGA 2011-based CPUs when it comes to power consumption, so they fall into third and fourth place.
The Phenom II X6 and FX bring up the rear, as they both use more power and underperform the Intel competition. It’s an unfortunate state of affairs for AMD, but the Piledriver core is being prepped for operation in the company’s next APU design. Hopefully, changes made to Bulldozer ameliorate some of what we’ve come to dislike about today’s FX.