In the 2017.10.09 update I added Asrock dual socket (EP2C602) support to the ipmi2json script (Configure Button). You need to stop any ipmi fan scripts. If you click on Configure on the Fan Settings page or run ipmi2json from the command line it will detect all available fans by setting them all to full speed then setting each point in the ipmi-raw command to 1/3. Then create a board.json in /boot/config/plugins/ipmi on the flash drive. Should look something like this but with actual fan names.
{
"ASRock": {
"raw": "00 3a 01",
"auto": "00 00 00 00 00 00",
"full": "01 64 64 64 64 64",
"fans": {
"FAN_POS1": "00",
"FAN_POS2": "00",
"FAN_POS3": "00",
"FAN_POS4": "00",
"FAN_POS5": "00"
}
},
"ASRock1": {
"raw": "00 3a 11",
"auto": "00 00 00 00 00 00",
"full": "01 64 64 64 64 64",
"fans": {
"FAN_POS1": "00",
"FAN_POS2": "00",
"FAN_POS3": "00",
"FAN_POS4": "00",
"FAN_POS5": "00"
}
}
}