Shortest code to throw SIGILL Background

We already have a challenge about throwing SIGSEGV, so why not a challenge about throwing SIGILL?

What is SIGILL?

SIGILL is the signal for an illegal instruction at the processor, which happens very rarely. The default action after receiving SIGILL is terminating the program and writing a core dump. The signal ID of SIGILL is 4. You encounter SIGILL very rarely, and I have absolutely no idea how to generate it in your code except via sudo kill -s 4 &lt;pid&gt;. 

Rules

You will have root in your programs, but if you don't want to for any reasons,  you may also use a normal user. I'm on a Linux computer with German locale and I do not know the English text which is displayed after catching SIGILL, but I think it's something like 'Illegal instruction'. The shortest program which throws SIGILL wins.
PDP-11 Assembler (UNIX Sixth Edition), 1 byte
9

Instruction 9 is not a valid instruction on the PDP-11 (in octal, it would be 000011, which does not appear on the list of instructions (PDF)). The PDP-11 assembler that ships with UNIX Sixth Edition apparently echoes everything it doesn't understand into the file directly; in this case, 9 is a number, so it generates a literal instruction 9. It also has the odd property (unusual in assembly languages nowadays) that files start running from the start, so we don't need any declarations to make the program work.
You can test out the program using this emulator, although you'll have to fight with it somewhat to input the program.
Here's how things end up once you've figured out how to use the filesystem, the editor, the terminal, and similar things that you thought you already knew how to use:
% a.out
Illegal instruction -- Core dumped

I've confirmed with the documentation that this is a genuine SIGILL signal (and it even had the same signal number, 4, all the way back then!)