I've just committed some changes to the diskless
boot code which allow to select the configuration
protocol (BOOTP or BOOTPARAM) in the system
configuration file.
2 new options are in effect:
NFS_BOOT_BOOTP: use BOOTP (allow for DHCP
   extensions if NFS_BOOT_DHCP is defined in addition)
NFS_BOOT_BOOTPARAM: use SUN bootparams
At least one of them must be defined now for diskless boot
to work. (otherwise you'll get an EADDRNOTAVAIL
error -- better ideas?)

I've added the options to a couple of the GENERIC
files now. I'll add them to the remaining GENERIC files
tomorrow.

best regards
Matthias