Hi,
It is interesting that the iMac described here (333MHz) seems not to have the atabus attachment problem that I have on my original Bondi-Blue iMac (233MHz) running NetBSD-5 or later.
It might be worth loading a new genfb kernel to see if you still get that issue. What drives do you have on your IDE busses? My setup is a little less standard, I think, since the motherboard isn't in a machine and the IDE goes to a SATA drive through an adapter which is master on the primary IDE channel.
John