Results: Power Consumption
Active Idle Power Consumption
Idle consumption is the most important power metric for consumer and client SSDs. After all, solid-state drives complete host commands quickly and then drop back down to idle. Aside from the occasional background garbage collection, a modern SSD spends most of its life doing very little. Enterprise-oriented drives are more frequently used at full tilt, making their idle power numbers less relevant. But this just isn't the case on the desktop, where the demands of client and consumer computing leave most SSDs sitting on their hands for long stretches of time.
Active idle power numbers are critical, especially when it comes to their impact on mobile platforms. Idle means different things on different systems, though. Pretty much every drive we're testing is capable of one or more low-power states, up to and including DevSlp. That last feature is a part of the SATA 3.2 host specification. And while it requires a capable SSD and a compatible platform, enabling DevSlp takes power consumption down to a very small number.
Given the ultra-low power enabled by DevSlp, I'd like even greater precision from our power measurements. Still, at active idle, the M5 and M6 drives demonstrate similar consumption.
PCMark 7 Average Power Consumption
If we log power consumption through a workload, even a relatively heavy one, we see that average use is still pretty close to the idle numbers. Maximum power may spike fiercely, but the draw during a PCMark 7 run is light. You can see the drives fall back down to the idle "floor" between peaks of varying intensity.
New flash and an updated controller pay off; the M6 outdoes Plextor's previous generation in our average power consumption test.
Despite the fact that the M6M is powered by the +3.3 V rail and the M6S uses +5 V, the two drives demonstrate near-identical readings.
Active idle kicks around the mid .4 W range, though on a Haswell-U-based system, DevSlp would drop that figure to .002 W or so, according to Plextor. The caveat is that it takes a significant amount of time to recover from this state.