The Intel SSD 660p SSD Review: QLC NAND Arrives For Consumer SSDs

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.

The Intel SSD 660p's power and thermal management feature set is typical for current-generation NVMe SSDs. The rated exit latency from the deepest idle power state is quite a bit faster than what we have measured in practice from this generation of Silicon Motion controllers, but otherwise the drive's claims about its idle states seem realistic.

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 Intel 660p has a slightly lower active idle power draw than the SM2262-based drives we've tested, thanks to the smaller controller and reduced DRAM capacity. It isn't the lowest active idle power we've measured from a NVMe SSD, but it is definitely better than most high-end NVMe drives. In the deepest idle state our desktop testbed can use, we measure an excellent 10mW draw.

The Intel 660p's idle wake-up time of about 55ms is typical for Silicon Motion's current generation of controllers and much better than their first-generation NVMe controller as used in the Intel SSD 600p. The Phison E12 can wake up in under 2ms from a sleep state of about 52mW, but otherwise the NVMe SSDs that wake up quickly were saving far less power than the 660p's deep idle.