Just flashed the latest 2M seabios text rom onto the PDIP-8 chip that came with the motherboard.
It boots! But, it says there's some device error (this is probably because the PS/2 port is broken, I was getting an error with stock bios too), and then the cpu fans go VVVRRRRRRRR, probably like double the full speed, it's super loud, like it's gonna blow up or something. Also, neofetch says the CPU is at 0mhz, instead of 3.7Ghz.
I tried switching the cpu fan jumpers, nothing changed. Both CPUs are Opteron 4284. Motherboard is from August 2013. Should I drop another $120 on another KCMA-D8 board, or is there anything else that I can try?
I'm not aware of any way to control fan speed through the boot firmware itself; it seems to start the fans at full speed at boot. The only way to quieten the fans is to use fancontrol, although that isn't ideal. I would swap out those fans with something quieter when it's at top RPM so you don't have to deal with fancontrol.
Note: I have a KCMA-D8 as well but it's very quiet since I have larger heatsinks/fans (120mm fans)