The ADATA XPG SX950 480GB SSD Review: In Search of Premium
by Billy Tallis on October 9, 2017 8:00 AM ESTPower 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.
Our ADATA XPG SX950 didn't seem to ever make use of the slumber power state; it draws about 0.8W with or without power management enabled. This is a relatively high active idle power draw for a SATA SSD, and the lack of deeper idle is unacceptable for mobile use.
The bright side of not using any deep idle states is that the ADATA XPG SX950 doesn't take any time to wake up; the 16µs latency we measured is pretty much all on the host side. Phison's SATA drives also do very well on this metric, and the rest all need more than half a millisecond to wake up.
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CheapSushi - Tuesday, October 10, 2017 - link
Next year with QLC it'll change. SATAIII is will still be useful for bulk drive SSDs coming. Yeah sure, if you're JUST a gamer and want only ONE drive for everything, it's a no-brainer on what direction to go. If you want just TWO drives, similar. But if you have more than that basic setup, SATAIII QLC SSDs are going to be perfect for bulk storage, while you have your OS and other main programs/software on an NVMe drive(s).MrSpadge - Monday, October 9, 2017 - link
Billy, you need to be less honest with your titles if you want people to actually read your review ;)RaistlinZ - Monday, October 9, 2017 - link
"In Search of Adequate"Lolimaster - Tuesday, October 10, 2017 - link
Years later and still nothing can compete with the 850 EVO 500GBmapesdhs - Wednesday, October 11, 2017 - link
This is how the exchange should go down when storage techs come up with a new SSD design and want approval to proceed:Tech: "We've designed a new SSD!"
Manager: "Is it better than the 850 EVO?"
Tech: "Umm, no."
Manager: "Go away."