This is a new one...  Sources from 1/28/03:

from './build.sh -D /steel/build/tree -R /steel/build/tars -u -T 
/usr/src/obj/tools release >& ./build.sh.log

[...]
making sure the kern library is up to date...
`libkern.a' is up to date.
creating bootxx_ffs from bootxx_ffs.sym...
-rw-r--r--  1 root  125  8096 Jan 28 15:49 bootxx_ffs
checking sizes for bootxx_ffs/bootxx_ffs.sym... MAXIMUM LOAD SIZE EXCEEDED 
(8096 > 7680)
*** Error code 1

The only other reference I can find is a recently opened PR from port-pmax...