Hiya!
  Got these two pdp11s, one an 11/23 (Ultrix-11 3.1) and the other an 11/84
(2.11BSD)

On the Ultrix machine, I can enter an assembly language program, assemble
it and run it fine.
amnesiac# cat hello.s
        mov     $1,r0
        sys     4
        a
        6
        sys     1
a:      <Hello\n>
amnesiac# od hello
0000000 000407 000022 000000 000000 000014 000000 000000 000000
0000020 012700 000001 104404 000014 000006 104401 062510 066154
0000040 005157 000000 000000 000000 000002 000000 000000 000000
0000060 000000 000000 000141 000000 000000 000000 000002 000014
0000100
amnesiac# ./hello
Hello
amnesiac#


But on the BSD machine, the exact same source program assembles differently
and crashes with Illegal instruction when I run it.
> cat hello.s
        mov     $1,r0
        sys     4
        a
        6
        sys     1
a:      <Hello\n>
> od a.out
0000000  000407 000022 000000 000000 000010 000000 000000 000000
0000020  012700 000001 104404 000014 000006 104401 062510 066154
0000040  005157 000000 000000 000000 000002 000000 000000 000000
0000060  000000 000000 000000 000004 000002 000014 000000 000006
0000100  000141
0000102
> ./a.out
Illegal instruction (core dumped)
>


Anyone know what I'm doing wrong?

thx
jake