“I tried this heatsink on my new Raspberry Pi 4, in comparison with no cooling, the Fan SHIM, and the POE HAT (which has an integrated fan).
With no load on the Pi, the CPU temperature was approx 59°C.
When I fitted the heatsink (which fit exactly into the space in the Pibow Coupe case) the CPU temperature quickly dropped to 52°C, but this was because the heatsink was cold. Over the course of 25 minutes, the CPU temperature graduall rose, eventually reaching 59°C again. I was able to carefully peel the heatsink off again, and I found that the heatsink had made good contact with the surface of the CPU.
I tried the Fan SHIM (which also fit within the Pibow Coupe case) and was easily able to reduce the CPU temperature to 45°C, but by default the fan runs as full speed and makes a noticeable amount of noise.
I also tried the POE HAT, which has the primary purpose of powering the Raspberry Pi over an Ethernet connection from a POE-compatible ethernet switch). The POE HAT includes an integrated fan which not only switches on and off as necessary, but also includes some speed control. This was also able to easily keep the CPU temperature below 45°C - by default the fan turns on at about 60°C, and turns off at around 45°C. As with the Fan SHIM, the fan can easily be heard in a quiet room, but the fan on the POE HAT also supports some speed control: by running the fan continuously at a lower speed the CPU temperature can be kept at a constant 45°C with no audible noise in a fairly quiet room.
It's a shame that the heatsink cannot be used in combination with any of the fan cooling solutions, since I think this could provide even better cooling, but it doesn't look like this would fit within the size constraints of the Raspberry Pi4 design.”
