I've been putting together a Raspberry Pi 4 Compute Module system. Although the Pi 4 has gotten better about heat generation over the years (software improvements, not so much hardware), I always stick a fan/heatsink on my Pi 4 modules. For the Pi CM4 I bought the following on Amazon (quick warning: do not buy this):
https://smile.amazon.com/dp/B092PMY7RC? ... ct_details
Foolish me, I didn't bother reading the reviews or even look closely at it. The price was cheap enough ($9 at the time) that I didn't give it a second thought. Turned out to be a waste of $9. There are several things wrong with this fan:
1. The thermal tape provided is not thick enough (and is the same thickness for all ICs, even though they are multiple heights).
2. The fan draws power from the GPIO pins (rather than the Fan connector provided on the CM4 I/O board). This pretty much means you can't install a HAT on your CM4 I/O board without a lot of extra wiring.
3. It uses up a GPIO pin on the header to do PWM fan speed control; this could conflict with a HAT.
4. To do PWM, you have to install software (I'm assuming this is the case; I never actually got that far with this fan, but I doubt that GPIO pin would do anything on its own).
5. The bolts weren't long enough to bolt this thing through the CM4 module onto the I/O board.
6. It didn't have spacers to go between the CM4 module and the I/O board (so even if the screws were long enough, it could damage your CM4 module if you tightened the screws down too much).
Okay, not a good purchase on my part.
The second time around, I purchased a Waveshare fan.
https://smile.amazon.com/dp/B0B3F63DGD? ... tails&th=1
It was $15, but resolves all the above issues. A little bit sleeker, too.
Usually when I buy stuff on Amazon, I immediately go to the 1-star reviews and see if I'm going to have problems with a product. This time, I forgot to do this ("How can you mess up a fan?"). Don't make the same mistake I did.
In the future, I will post my experiences with the Raspberry Pi Compute Module 4 system I'm building.
Cheers,
Randy Hyde