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.

Darrin

dbj@netbsd.org writes:

> Is there a keyboard combination that can be pressed
> to access ddb on a 500mhz dual usb ibook?
> It's not listed in the ddb(4) man page.
> 
> I've tried several options, including:
>   command-power
>   command-option-power
>   command-ctrl-escape
>   option-ctrl-escape
>   command-ctrl-power (this causes an instant reboot)
> 
> I can enter ddb using the -d boot flag, so I have
> verified that ddb is compiled into the kernel.
> 
> Thanks,
> 
> Darrin