Power Management

Real-world client storage workloads leave SSDs idle most of the time, so the active power measurements presented earlier in this review only account for a small part of what determines a drive's suitability for battery-powered use. Especially under light use, the power efficiency of a SSD is determined mostly be how well it can save power when idle.

SATA SSDs are tested with SATA link power management disabled to measure their active idle power draw, and with it enabled for the deeper idle power consumption score and the idle wake-up latency test. Our testbed, like any ordinary desktop system, cannot trigger the deepest DevSleep idle state.

Idle power management for NVMe SSDs is far more complicated than for SATA SSDs. NVMe SSDs can support several different idle power states, and through the Autonomous Power State Transition (APST) feature the operating system can set a drive's policy for when to drop down to a lower power state. There is typically a tradeoff in that lower-power states take longer to enter and wake up from, so the choice about what power states to use may differ for desktop and notebooks.

We report two idle power measurements. Active idle is representative of a typical desktop, where none of the advanced PCIe link or NVMe power saving features are enabled and the drive is immediately ready to process new commands. The idle power consumption metric is measured with PCIe Active State Power Management L1.2 state enabled and NVMe APST enabled (when supported).

Active Idle Power Consumption (No LPM)Idle Power Consumption

(idle power)

Idle Wake-Up Latency

(idle wake-up)

Mixed Read/Write Performance Conclusion
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  • Billy Tallis - Friday, December 15, 2017 - link

    The ATSB tests are Windows-based, and the synthetic tests are on Linux with fio. I can't really create a RAM disk large enough to properly run the ATSB tests (at least not on this system), but I'll look into running the synthetic tests against a RAM disk.
  • tuxRoller - Saturday, December 16, 2017 - link

    Thanks so much for the response and clarification.
    I'll keep an eye out for that ramdisk comparison:)
  • Chaser - Friday, December 15, 2017 - link

    In other words, if you are the enthusiast gamer person like many of the people that read this site, you're throwing money away buying this for your gaming system.
  • jabber - Friday, December 15, 2017 - link

    You are pretty much throwing away money investing in anything faster than a 850EVO in a gaming rig.
  • eek2121 - Sunday, December 17, 2017 - link

    Not really, as a gamer, you should not only be looking at performance, but at reliability as well. Ironically I say this NOT because the 8xx EVO is crap (my 840 evo still has 93% life left and that's despite being used as a system drive for many years), but because my 960 evo has had a metric ton of degradation in the 6 months I've owned it.
  • Klimax - Sunday, December 17, 2017 - link

    Only if one has few games. There's better solution: 16GB of RAM + large regular HDD (WD Black and similar, their sequential reads are very good). Only initial load will be noticeable. (Anytime after that, caching will take care of that)
  • CheapSushi - Friday, December 15, 2017 - link

    Umm, what? Optane would be the better drive in every single way for OS and general usage. If you were going to get ONE main drive, it should be Optane.
  • ddriver - Friday, December 15, 2017 - link

    Sure, but is 0.01% faster in real world performance worth being 300$ more expensive? If you are going with one main drive, you better get better capacity than performance you can't make any use of.
  • tricomp - Saturday, December 16, 2017 - link

    Here is what Tom wrote about Optane OS drive : "You will see and feel a performance benefit just by using the Optane SSD 900P as your operating system drive. The feel of the system changes even if you’re replacing a high-performance NVMe SSD. You will notice the increased responsiveness immediately and then gradually become accustomed to it. In our experience, you will take the performance for granted until you work on a slower PC. Then you'll wish it had an Optane SSD." Its main advantage - 4K read performance - makes it OS king
  • eek2121 - Sunday, December 17, 2017 - link

    "Tom" has been gone for a long time. Tom's hardware, much like AnandTech, has simply become a vehicle for Purch Ads (sadly). The AnandTech or Tom's Hardware of today have absolutely nothing to do with the original founders/sites. I don't mean to sound anti-corporate (because I'm not), but Purch has allowed pretty much all of their sites to degrade to the point where they have become irrelevant. I mean no disrespect to any AT folks either. I'm sure they bust their asses off. However, IMO, Purch has taken some very valuable brands and driven them into the ground in a desperate reach for revenue.

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