Real Time Audio Output, what am I doing wrong?

Hardware Arduino Due
8

What about a Raspberry Pi but running Bare Metal not Linux.
http://www.raspberrypi.org/phpBB3/viewforum.php?f=72&sid=a37b803b1be563f5e071ca950c32b2b8
That runs at between 700 to 1000MHz depending on the clocking options.