ATTO's Disk Benchmark is a quick and easy freeware tool to measure drive performance across various transfer sizes.

ATTO Performance

The lower write speed of the 256GB RD400 is clearly visible. All three models show essentially no performance scaling from 16kB to 64kB transfer size but only reach full performance for 512kB or larger transfers.


AS-SSD is another quick and free benchmark tool. It uses incompressible data for all of its tests, making it an easy way to keep an eye on which drives are relying on transparent data compression. The short duration of the test makes it a decent indicator of peak drive performance.

Incompressible Sequential Read PerformanceIncompressible Sequential Write Performance

The 256GB RD400 lags a bit behind the competition for read speed and all three are near the bottom of the PCIe segment for write speed.

Idle Power Consumption

Since the ATSB tests based on real-world usage cut idle times short to 25ms, their power consumption scores paint an inaccurate picture of the relative suitability of drives for mobile use. During real-world client use, a solid state drive will spend far more time idle than actively processing commands. Our testbed's PCIe link state power management support is broken, so only active idle power consumption is reported. This is realistic for most desktop scenarios, but a properly configured mobile system can potentially save power by enabling link power management for PCIe and SATA.

Active Idle Power Consumption (No ALPM)

The 12V to 3.3V conversion done by the PCIe to M.2 adapter card bundled with the RD400 is providing some overhead to idle power, but most of this poor showing comes down to a lack of usable PCIe power management on common desktop platforms.

Mixed Read/Write Performance Final Words


View All Comments

  • tarqsharq - Wednesday, May 25, 2016 - link

    Interesting article as always. I had been hoping for a larger price gap between this and the Samsung 950 Pro. At current prices, I think the choice is fairly obvious unless you need a 1TB SSD. Reply
  • Chaitanya - Wednesday, May 25, 2016 - link

    You have a choice of Sandisk X400 as well if you want 1TB capacity in M.2 form factor. Reply
  • edzieba - Wednesday, May 25, 2016 - link

    There's also the OEM version of the OCZ drive, the Toshiba XG3, which is also available in a 1TB m.2 SKU. Reply
  • Lord of the Bored - Thursday, May 26, 2016 - link

    And who DOESN'T need a 1TB SSD? Reply
  • MrSpadge - Friday, May 27, 2016 - link

    I think you're mixing up "want" and "need". Reply
  • DanNeely - Wednesday, May 25, 2016 - link

    "Unlike most cheap adapter cards, the RD400's adapter draws power from the PCIe slot's 12V supply and converts it to the 3.3V required by the M.2 drive."

    PCIe slots provide 10W of 3.3V power directly. (I believe this was originally done to make converting legacy cards via a bridge chip easier.) Why would the card need to do any DC-DC conversion?
  • Byrn - Wednesday, May 25, 2016 - link

    I'd assume that if they convert they can get cleaner 3.3V than if they use the feed through the PCIe slot, or that they can design in better resilience to sudden power demand changes...

    Basically, by converting I would have thought they can better fit the power supplied to the drive to the demands it makes.
  • digitalgriffin - Wednesday, May 25, 2016 - link

    You can filter any volt feed with enough capacitors. But you lose power efficiency when you do. Reply
  • Alexvrb - Wednesday, May 25, 2016 - link

    Yeah but they're filtering the power either way so converting from 12V -> 3.3V is less efficient than using 3.3V to start with. But getting back to what Byrn was saying... Byrn, they don't have a choice: This drive draws too much power to use the 3.3V supply.

    Look at idle power figures in this article. ~2.5W @ 12V. At 3.3V that would already be pushing it (right around 9W already). Under a load it's going to draw too much. So they had to use the 12V rail.
  • Wardrop - Wednesday, May 25, 2016 - link

    2.5 watts is 2.5 watts. If it's a higher voltage, it's less amps, and vice versa. I think you've confused watts with amps? Reply

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