Thermal Throttling

Due to the compact form factor, M.2 drives lack the ability to cool themselves and usually have to rely on passive airflow instead. All vendors include some form of thermal throttling on their drives as a safeguard, which limits throughput once a certain temperature is exceeded.

On this page, we will investigate whether the tested drive has such a mechanism, how high temperatures get, and what effect this has on performance. We will test the drive in a typical case and the M.2 slot between the CPU and VGA card. A second data point shows the result with a 120 mm fan directly blowing on the tested drive. Each of the charts has time moving from left to right, with the blue line displaying transfer speed in MB/s and the red line showing the temperature in °C (measured using SMART).

Please note that the following charts not only have the red line indicating temperature, but also the green line. Crucial has two thermal sensors on the P5, which is great for all the sensor buffs out there. Green is the temperature of the controller, and red seems to be the temperature of the flash.

Reads

In a pure read scenario, the drive throttles after 200 seconds. This is quite surprising—I can't remember the last time I've seen an M.2 SSD throttle with just reads.

Writes

When heavily loaded with writes, throttling starts even quicker than with reads—after around two minutes of writing at full speed.

Thermal Limits

The tests above represent a worst-case scenario for the SSD since we're running it at maximum speed for an extended period of time. Beyond that, it becomes important to look at how storage performs when it's under lighter load, which is the case with many consumer applications. For this test, we're sending a fixed-rate stream of data to the drive until temperatures have stabilized. As long as there is no thermal throttling, we'll increase the data rate and chart it below.

Thermal Image & Hot Spot

We recorded a thermal image of the running SSD as it was completing the write test. The hottest part reached 106°C, which matches the drive's own thermal reporting almost exactly. Nice to finally see accurate thermal monitoring on an SSD.