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.
| Team Group MP34 512GB NVMe Power and Thermal Management Features | |||
| Controller | Phison PS5012-E12 | ||
| Firmware | ECFM12.2 | ||
| NVMe Version | 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 new 12.2 firmware for the Phison E12 doesn't bring any change to the list of supported power management features. The maximum power draw declared by the MP34 for each of its three active power states is actually a few mW higher than what the Gigabyte Aorus RGB claims, but other than this the power state table hasn't been tweaked.
| Team Group MP34 512GB NVMe Power States | |||||
| Controller | Phison PS5012-E12 | ||||
| Firmware | ECFM12.2 | ||||
| Power State | Maximum Power | Active/Idle | Entry Latency | Exit Latency | |
| PS 0 | 8.12 W | Active | - | - | |
| PS 1 | 6.40 W | Active | - | - | |
| PS 2 | 5.54 W | Active | - | - | |
| PS 3 | 49 mW | Idle | 2 ms | 2 ms | |
| PS 4 | 1.8 W | 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, and depending on which NVMe driver is in use. Additionally, there are multiple degrees of PCIe link power savings possible through Active State Power Management (APSM).
We report three 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. Our Desktop Idle number represents what can usually be expected from a desktop system that is configured to enable SATA link power management, PCIe ASPM and NVMe APST, but where the lowest PCIe L1.2 link power states are not available. The Laptop Idle number represents the maximum power savings possible with all the NVMe and PCIe power management features in use—usually the default for a battery-powered system but rarely achievable on a desktop even after changing BIOS and OS settings. Since we don't have a way to enable SATA DevSleep on any of our testbeds, SATA drives are omitted from the Laptop Idle charts.
Note: We recently upgraded our power measurement equipment and switched to measuring idle power on our Coffee Lake desktop, our first SSD testbed to have fully-functional PCIe power management. The below measurements are all new this month, and are not a perfect match for the older measurements in our previous reviews and the Bench database.
The Phison E12 controller continues to have pretty good power management. The active idle power consumption and the deepest laptop idle power states are best in class, but Silicon Motion's SM2262(EN) controllers can usually reach a deeper idle power level on most desktops.
The idle wake-up latencies measured from the Phison E12 drives including the Team MP34 are pretty close to what the drive promises to the OS. The desktop idle state corresponds to the drives NVMe Power State 3, and the laptop idle is the drive's Power State 4. Most of the other controllers take about the same amount of time to wake up from either the desktop or laptop idle states, indicating that they aren't smart enough to disable their deepest (slowest) idle power state when the requisite PCIe link states are unavailable. This leaves the Silicon Motion drives in particular at a potential disadvantage on a desktop that's configured to use some power savings.
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