Throttling without heatsink
Before we take a look at the effectiveness of the different heatsinks, we first tested the Samsung 960 Pro 512GB as is, without mounting a heatsink. We always measure the temperature of the memory chips as well as the temperature of the controller; the latter is usually higher.
After two custom runs in Atto Disk Benchmark we come at a total of 111 degrees Celsius for the controller and 71 degrees for the nand-chips. This lead to serious thermal throttling – the read speed got bumped down from more than 3 GB/s to about 2.4 GB/s, while writing was done at less than 1.7 GB/s. At full speed it should be capable of reaching speeds well over 2 GB/s.
We also performed all tests with the airflow of a 92mm-fan at a distance of a casefan in the average case. Without heatsink this resulted in a maximum controller temperature of 79 degrees, low enough to prevent serious throttling. However, in practice there will often be barely any airflow in the place where you mount an m.2-SSD, which means that a good heatsink definitely has an added value.