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.

Silicon Power P34A80
NVMe Power and Thermal Management Features
Controller Phison PS5012-E12
Firmware ECFM12.1
Feature Status
1.0 Number of operational (active) power states 3
1.1 Number of non-operational (idle) power states 2
Autonomous Power State Transition (APST) Supported
1.2 Warning Temperature 70 °C
Critical Temperature 90 °C
1.3 Host Controlled Thermal Management Supported
 Non-Operational Power State Permissive Mode Not Supported

The supported power features on the Silicon Power P34A80 are the same as on the earlier 11.0 firmware. The maximum power figures for the active power states are the same relatively high limits found on the Corsair Force MP510, rather than the lower values seen on our earlier reference design engineering sample from Phison.

Silicon Power P34A80
NVMe Power States
Controller Phison PS5012-E12
Firmware ECFM12.1
Active/Idle Entry
PS 0 10.73 W Active - -
PS 1 7.69 W Active - -
PS 2 6.18 W Active - -
PS 3 49 mW Idle 2 ms 2 ms
PS 4 1.8 mW Idle 25 ms 25 ms

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.

Active Idle Power Consumption (No LPM)Idle Power Consumption

The P34A80 has slightly higher active idle power consumption than the Corsair MP510, but still lower than any high-end NVMe drive using a competing controller. The idle power consumption is unchanged, leaving the Phison E12 with good power management but not quite the best achievable on our desktop testbed.

Idle Wake-Up Latency

The P34A80 is slightly slower to wake up from idle than the Corsair MP510, but at under 3ms it's still plenty fast, and otherwise is only really beat by drives that are unable to reach a deep idle state on our desktop testbed.

Mixed Read/Write Performance Conclusion


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