HiFive Unmatched cooling

Hi all, I just bought (well, pre-ordered I guess) :slight_smile: The an HiFive unmatched through Mouser. Something that confuses me a little right now as I’m trying to figure out what other parts I’m going to need for the system is cooling.

Some of the images of the Unmatched suggest some tiny fan/heatsink combination that’s sort of stuck on the chip with some kind of clip? The cooling solution however isn’t mentioned on a parts list, and not all images of the board seem to have those cooling solutions shown either.

So I guess my question is twofold:
a) What (if any) cooling solution is provided in the box with the Unmatched
b) What mounting mechanism(s) are available on the board itself? Will there be holes to mount something with a decent pressure? Are there protrusions that can be used to clip something to?

My overall goal with this build is to have a usable box to port some software (Godot engine to be specific) to RISC-V so I’d really like to be able to build something that can live on my desk and not be too annoying acoustically if at all possible. :slight_smile:

I haven’t seen an Unmatched in the flesh but the photos look like the same cooling solution as the Unleashed.

The yellow plastic thing seems to clip under the chip package and hold a finned passive heatsink against the chip – I haven’t attempted to disassemble this part. I believe it was initially hoped with the Unleashed that would be enough cooling, but it turned out it wasn’t. The fan is attached by four screws that grip onto the heatsink fins. I’ve taken the original fan off and replaced it when it got noisy after a couple of years.

At the around 6W maximum consumption of the Unleashed you don’t need a lot of cooling. The Raspberry Pi 4 is very similar power use and they just let it thermal throttle out of the box :slight_smile: There isn’t any thermal throttling or even temperature measurement on the FU-540, so the fan is needed. I assume the FU-740 has added that feature.

According to an app on my iPhone “Decibel Meter” (by Xiangyi Liu) a quiet bedroom in my rural house has a background level of 22 dB (most of which is birds outside). The HiFive Unleashed 10cm from the phone increases this to 28 dB (both averaged over a minute). Moving to my home office with my unusually quiet PC (I made an effort with it) I get 38 dB without or without the HiFive. In the quiet bedroom I can hear the HiFive Unleashed fan from 2.5m away but not from 3.5m. In the home office I can’t detect it from 1m. In an office with air conditioning or similar you wouldn’t hear it at all. I suspect if you mount an Unmatched inside a PC case without any PC fans you also wouldn’t hear it at all, even in the quietest room (an ATX power supply would be louder).

Thank you for the information! I’ll just see what ships then. Do you think SiFive will sell after-market cooler clips if I try to customize mine and euh… fail miserably? :slight_smile: