Try command-option-escape on your G4 tower.

I think the /dev/ttyE0 vs. /dev/console issue is not specific to
macppc.  The code to check if the keystroke is coming from the console
is in the generic wscons code.  Besides that observation, I don't know
the details of why things are the way they are.

Also, if your console is not secure, I really don't
recommend running DDB on it.

Darrin

Derek Peschel <dpeschel@eskimo.com> writes:

> > After some debugging, I determined that the keystroke
> > is in fact command-option-power.  However, it must be
> > entered on /dev/console.  After editing /etc/ttys to
> > turn /dev/ttyE0 off and /dev/console on, I am able
> > to enter DDB without problem.
> 
> My machine (G4 tower) doesn't have a power key. It has
> power buttons on the monitor and CPU, but nothing on
> the keyboard.  Am I stuck?
> 
> It _does_ have an interrupt switch... is there some reason
> why ddb can't just use that?  Then we wouldn't have to go
> messing with virtual-console functionality by turning off
> /etc/ttyE0 (not that we _support_ virtual consoles,
> but it's the principle of the thing).
> 
> Messing with /dev/console and /dev/ttyE0 runs into another
> problem: the "security" setting for /dev/console in /etc/ttys
> is special; it determines whether the root password must be
> entered when booting in single-user mode.  So you can't just
> blindly start using /dev/console instead of /dev/ttyE0 and
> expect things to work the same as before.
> 
> -- Derek