The MX3S is a very good choice for building an S370 setup.
- latest BIOS compatible with Tualatin;
- simple mod for pins and sockets;
- LAN
- boot from USB (Doesn't really work, but still. 😀 )

But very strange CPU temperature readings - the environment plus 3-4 degrees Celsius, weakly dependent on the load. For "some reason", Aopen engineers installed a thermistor in the socket and connected the CPU temperature diode in parallel with it. SIO input configured correctly as "Thermaldiode P2"
And two thermistors were placed near the SIO, since one of them is disabled in the BIOS. Otherwise, monitoring programs would assign it "CPU temperature"
You just need to bring the circuit to the datasheet on the SIO.
Change the resistor from Vref to 30kΩ and replace the thermistor in the socket with a capacitor.