Results: Power Testing
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 the DevSlp stuff we covered on the previous page.
Idle power consumption is stated as up to .4 W maximum by Samsung, but I see a steady .28 W each for the 128, 256, and 1024 GB 850 Pro. Rounding gives the 256 GB model an extra hundredth.
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.
All three capacities peak between 2 and 3 W, and each drops down to .3 W in between jobs. Because each drive comes equipped with a different amount of flash, they don't line up exactly. But it's easy to see that the 850 Pro is easy on power, even during heavy use.
The maximum power consumption of Samsung's 1 TB 850 Pro is around 3 W. Exact figures for the other capacities are given. The transition is smooth, though. I believe that different die sizes are being used for the smaller drives. But without knowing more about V-NAND, only Samsung's tight-lipped engineers know for sure.
