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Power Testing: Now With 73% More DevSlp

JMicron Returns: The JMF667H Controller On Four Reference SSDs
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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 3.1 host specification. And while it requires a capable SSD and a compatible platform, enabling DevSlp takes power consumption down to a very small number.

Interestingly, I measure consistently different active idle states for the JMicron reference drives. The two 128 GB configurations land in the .4 W range, while both 256 GB SSDs idle closer to .2 W. For drives with twice as much NAND, that's seemingly weird.

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.

At this point, it's tempting to suspect something is wrong. But it's not. The two 256 GB JMF667H-based drives again use substantially less power (on average) through the run, thanks largely to the low idle power consumption already observed.

After a lot of power testing, logging, and Excel work, we end up with the above chart. It's not particularly readable, but that just lends to its air of mystery, right? We've heard plenty of readers like Chris Angelini's power charts in his CPU reviews; this is something similar for you.

But it's beyond me why the disparity in idle power use is so pronounced. This has to be an artifact of JMicron's JMF667H-based reference platforms and the on-board components though, though. To conclude then, these drives appear super efficient overall, and it bothers me that the drives are so different at idle. But the outcome doesn't truly become significant until we can start getting our hands on more retail hardware employing JMicron's processor.

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