Results: Power Consumption
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 far 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.
It might sound funny, but this is the page we were waiting for. Optimized efficiency is purportedly the goal Silicon Motion has in mind for this platform. The company demonstrates active power consumption just behind what we've measured from most of the Samsung drives. The 128 GB 840 Pro maintains its first-place finish, though the reference SM2246EN-based SSD breaks out an impressive .32 W result.
Keep in mind that this is an active idle state, and that drives like Silicon Motion's are capable of dropping into much lower power states. Also, we have to point out that measuring true power consumption is a tricky business, and that there is likely a 5% or so margin of error.
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. Max power may spike fiercely, but the usage seen during a PCMark 7 run is pretty light. You can see the drives fall back down to the idle "floor" between peaks of varying intensity.
I picked the 120 GB 840 EVO to pit against Silicon Motion's test mule. Is it a fair comparison? Not necessarily. Samsung's triple-level cell flash needs more juice than Toshiba's MLC NAND, and it's reasonable to expect higher power consumption when these drives are juggling more taxing workloads. Moreover, the SM2246EN-based SSD uses twice as many dies, too.
Silicon Motion uses almost exactly the same power as Samsung's sample, but generally uses a lot less while working on Futuremark's tests.
And that performance is good enough for an average PCMark 7 power figure of .55 W, which takes the top spot from the 840 Pro by a nose.
Maximum Observed Power Consumption
It's even better news that maximum power consumption isn't a critical specification for most desktop workloads. In the enterprise space, yes. This information goes into the calculation for total cost of ownership. But in a client environment, you shouldn't be seeing these numbers for more than short bursts.
In exchange for those compelling average power numbers, Silicon Motion's reference drive exhibits the highest measured maximum power consumption of any 128 GB-class SSD. That's likely a side effect of Toshiba's Toggle-mode flash. With all of those dies firing in parallel, maximum power is usually a function tied to the NAND, even if the controller can use a lot of juice as well.