My experience with the RPI4 suggests a heat sink on the CPU is a really good idea. So I bought the first heat sink Amazon suggested. It is about 1 cm tall and is tight fit to the Shake board.
I put a bit of vinyl tape on the underside of the shake board just in case. Any concerns?
What I am finding with the new install is a slight “tone” at 2 Hz and 4 Hz and I wonder if this might be the cause. I guess (I will have to change the heat sink to a smaller one to find out).
if you filter the wave form for 1-5 Hz you can see this:
without filtering it’s like this (not the same segment):
I have more heat sinks on order so I can try a smaller one - or grind this one down … FWIW - this is running at 1000 Mbps ethernet speed.