Benchmark Results: Power Consumption And Efficiency
Normally, we’d run Prime95 to determine maximum load power consumption and then PCMark Vantage to chart out consumption over time. However, a max figure isn’t really relevant here, and Vantage simply won’t run on our multi-socket configs. SYSmark Preview 2007 is populated by old, outdated software that wouldn't exploit threading in a way we could tie into a workstation story. So, I turned to LightWave 3D 9.6. The frame rendering process taxes available CPU cores and takes long enough for us to measure average power use.
The results are pretty gosh-darned telling. Not surprisingly, the lowest-power solution is a single Core i7-980X. However, the one CPU also takes the longest to finish frame eight of our rendering workload.
Two Xeon W5580s (130 W TDP processors) are actually the most power-hungry—and they don’t even finish the fastest. That honor goes to a couple of Xeon X5680s (also 130 W CPUs).
Our Extech logger sampled power every two seconds, making it easy to gauge the exact time for frame eight to render completely. We turn that time, in seconds, into its fraction of an hour, and then multiply by the average power use during the run.
It turns out that, while a single Core i7-980X is a great way to improve the efficiency of your workstation versus a pair of quad-core CPUs like the Xeon W5580s (despite the fact that the two Xeons are faster), a couple of Xeon X5680s turn that conclusion topsy-turvy. They get our workload finished fast enough that the elevated power is more than compensated for by increased performance.
Of course, this applies exclusively to usage models that are threaded. Once you hit an app that isn’t threaded, or less-optimally threaded, you won’t see the improved performance needed to justify higher power use. Instead, you’ll need to rely on Intel’s power gating to shut down unused pieces of each Xeon processor to prevent idle power use from skewing the overall efficiency picture.