OpenBSD 6.0 cannot boot on PowerMac 11,2

Hi.

I've just installed OpenBSD on my PowerMac 11,2. The install was
successfully done, but when i try to boot it, then in the middle of the
boot, it stops with the following message:

smu0 at mainbus0: cannot map smu-doorbell gpio

and then it stops and freezes. Slowly after this, the fans in the
machine are roars up and they begin to blow like hell.

Any ideas on this?

- TCH