My 1GHz has loud, full-blast, max rpm, high-speed, constantly spinning fan. After reading of jholt5638's success by removing modem, I just finished trying it. I guess the mainboard is damaged, because removed modem and reset-all did not result in changed fan behaviour. But I did confirm:

OpenBSD/macppc Boot device considerations:

ide0 (cdrom) is valid as a root drive only if no hard drives are connected to the Ultra bus.