Hello,

> ofwboot is located in the root FFS. OF loads bootxx from blocks
> specified by the partition map, bootxx loads ofwboot in FFS by
> struct bbinfo set by installboot(8), and ofwboot loads kernel in root
> file system. There is only ~8kbytes space at the top of FFS partition,
> and that's the reason why the secondary bootloader is used.
Hmm, the hp300 port uses something similar but doesn't need anything like bootxx - instead partition a begins at block 63 or so to leave room for the boot loader at position 0 ( it is considerably larger than 8KB and mimics a HP LIF filesystem which the boot PROM recognizes )
So I think there's more to it than just free space at the top of FFS partitions.

have fun
Michael