On today's sup, a make from allsrc/src/lib results in:
...
.../allsrc/src/lib/libc/arch/mips/sys/brk.S: Assembler messages:
.../allsrc/src/lib/libc/arch/mips/sys/brk.S:38: Fatal error: Unknown opcode: `amstr("from: @(#)brk.S 8.1 (Berkeley) 6/4/93")'
Alas, I know no pmax assembly so I can't go much further with this.
-- Todd