Power Consumption - The Xbox One

Power Consumption

As always I ran the Xbox One through a series of power consumption tests. I’ve described the tests below:

Off - Console is completely off, standby mode is disabled
Standby - Console is asleep, can be woken up by voice commands (if supported). Background updating is allowed in this mode.
Idle - Ethernet connected, no disc in drive, system idling at dashboard.
Load (BF4) - Ethernet connected, Battlefield 4 disc in drive, running Battlefield 4, stationary in test scene.
Load (BD Playback) - Ethernet connected, Blu-ray disc in drive, average power across Inception test scene.
CPU Load - SunSpider - Ethernet connected, no disc in drive, running SunSpider 1.0.2 in web browser.
CPU Load - Kraken - Ethernet connected, no disc in drive, running Kraken 1.1 in web browser

When I first saw the PS4’s idle numbers I was shocked. 80 watts is what our IVB-E GPU testbed idles at, and that’s with a massive 6-core CPU and a Titan GPU. Similarly, my Haswell + Titan CPU testbed has a lower idle power than that. The Xbox One’s numbers are a little better at 69W, but still 50 - 80% higher than I was otherwise expecting.

Standby power is also surprisingly high for the Xbox One. Granted in this mode you can turn on the entire console by saying Xbox On, but always-on voice recognition is also something Motorola deployed on the Moto X and did so in a far lower power budget.

The only good news on the power front is really what happens when the console is completely off. I’m happy to report that I measured between 0.22 and 0.45W of draw while off, far less than previous Xbox 360s.

Power under load is pretty much as expected. In general the Xbox One appears to draw ~120W under max load, which isn’t much at all. I’m actually surprised by the delta between idle power and loaded GPU power (~50W). In this case I’m wondering if Microsoft is doing much power gating of unused CPU cores and/or GPU resources. The same is true for Sony on the PS4. It’s entirely possible that AMD hasn’t offered the same hooks into power management that you’d see on a PC equipped with an APU.

Blu-ray playback power consumption is more reasonable on the Xbox One than on the PS4. In both cases though the numbers are much higher than I’d like them to be.

I threw in some browser based CPU benchmarks and power numbers as well. Both the Xbox One and PS4 ship with integrated web browsers. Neither experience is particularly well optimized for performance, but the PS4 definitely has the edge at least in javascript performance.

Power consumption while running these CPU workloads is interesting. The marginal increase in system power consumption while running both tests on the Xbox One indicates one of two things: we’re either only taxing 1 - 2 cores here and/or Microsoft isn’t power gating unused CPU cores. I suspect it’s the former, since IE on the Xbox technically falls under the Windows kernel’s jurisdiction and I don’t believe it has more than 1 - 2 cores allocated for its needs.

The PS4 on the other hand shows a far bigger increase in power consumption during these workloads. For one we’re talking about higher levels of performance, but it’s also possible that Sony is allowing apps access to more CPU cores.

There’s definitely room for improvement in driving down power consumption on both next-generation platforms. I don’t know that there’s huge motivation to do so outside of me complaining about it though. I would like to see idle power drop below 50W, standby power shouldn’t be anywhere near this high on either platform, and the same goes for power consumption while playing back a Blu-ray movie.

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