The ADATA XPG SX8200 & GAMMIX S11 NVMe SSD Review: High Performance At All Sizes

Power Management Features

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.

For many NVMe SSDs, the closely related matter of thermal management can also be important. M.2 SSDs can concentrate a lot of power in a very small space. They may also be used in locations with high ambient temperatures and poor cooling, such as tucked under a GPU on a desktop motherboard, or in a poorly-ventilated notebook.

Our samples of the ADATA XPG SX8200 use an older firmware revision than the GAMMIX S11 sample, but the power and thermal management features are the same between the two versions. ADATA's first generation of NVMe drives using the SM2260 controller didn't support Autonomous Power State Transitions, so in practice their idle power states would usually go completely unused. The warning and critical temperature thresholds are also 8 °C higher than on the SX8000.

The new drives with the SM2262 controller not only make the idle power states usable out of the box with most operating systems, they have significantly improved those idle power states: PS3 consumption has gone from 70mW to 45mW and the transition latencies are about an order of magnitude faster. (The SX7000/GAMMIX S10 firmware actually advertised even faster transitions, but without APST support that hardly matters.)

Note that the above tables reflect only the information provided by the drive to the OS. The power and latency numbers are often very conservative estimates, but they are what the OS uses to determine which idle states to use and how long to wait before dropping to a deeper idle state.

Idle Power Measurement

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 if supported.

The active idle power consumption of the ADATA SX8200 and GAMMIX S11 is in line with other SM2262 SSDs, and about 30% lower than the SM2260-based predecessors. Thanks to the addition of NVMe APST support, the newer drives actually get to use their deepest idle states, putting them around 10mW compared to the 600+ mW used by their predecessors.

Now that deep sleep states are actually being used, it's a given that the newer ADATA drives have non-trivial wake-up latencies. The SX8200 and GAMMIX S11 are relatively slow to wake up compared to the drives that idle in the 70-100mW range instead of the 10mW we get from the SM2262. However, the new ADATA drives are about 10ms faster to wake up than the other SM2262 drives we've tested.