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. As a safeguard, all vendors include some form of thermal throttling on their drives, 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, in the M.2 slot between the CPU and VGA card. A second data point shows the result when a 120 mm fan is blowing directly 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).

Reads

In a pure read scenario, the drive doesn't throttle at all.

Writes

Without a fan, the drive will start throttling once its internal temperature monitoring reports more than 70°C. The spikes before that are just the drive's normal behavior for writes; we can see the same spikes for the cooled drive, which doesn't throttle. If you look closely, you can see that the height of the spikes changes for the uncooled drive when its temperature exceeds 70°C—that's the throttling I'm talking about.

Thermal Image & Hot Spot

We recorded a thermal image of the running SSD as it was completing the write test. The hottest part reached 92°C, which is significantly higher than what the drive's own SMART temperature monitoring reports.