Booting FreeBSD on a Macintosh?

[Volker Nebel]

Dear all,

looking for a good a computer I bought a Macmini 6,1 with Intel Core i5 
last summer, then installed Ubuntu (for amd64) on it and now came back to 
FreeBSD (already running on my laptop). Having installed this, the macmini 
does not boot anymore, unfortunately. It only shows a blinking question 
mark in a folder symbol.
    I searched the web for hints and found half a dozen of pages describing 
how to run both, Mac OS and FreeBSD. One page recommanded to issue
"gpart bootcode -b /boot/pmbr -p /boot/gtpboot -i 1 ada0" after the 
installation and before reboot, but this didn't help. I found the hint to 
use FreeBSD for i386 - same result. (And it did boot Ubuntu for amd64.) 
Someone else recommanded to use MBR partitioning scheme instead of GPT, 
but the Partition Editor of the FreeBSD Installer returns "Error Invalid 
Argument" when I try to Create a partition of type freebsd-boot and size 
64k or 512K.
    Can anybody help? How can I install FreeBSD 9.2 on a Macmini and boot?

Best regards,
Volker