Some fans have a minimum RPM they won't go below, it depends on the fan revision/vendor. We had to source like 3-4 fan vendors during the pandemic all with slightly different fan controllers.
You can test this with the -fan_pwm_hi 1 parameter. That will force the PMW controller to not output anything and make the fan either not spin or spin at its lowest speed possible.
Tested it, thanks!
The fan is the type that will not run slower than about 1800rpm. I have double-tested this by connecting a different fan. An 80mm Noctua PWM fan will run intermittently, while the stock fan never goes below 1800rpm.
Could you please let me know which fan would be ideal for the Apollo ASICs ? I'm happy to buy some and replace them if they are now available.
I would like a high quality fan that can reach high speed and air flow when required, but turns off completely (or at least so slow that it is very silent) when the miner temperature is below the -fan_temp_low setting.
The cooler fan in my batch 1 standard unit also never goes below 1800 RPM. Has anybody made good experience with replacing the stock fan with a Noctua NF-A8 PWM or a NF-R8 redux-1800 PWM yet on the Apollos? These should be able to turn at least as low as 325 RPM.