HMP and cpu freq driver patches are included.
Simply copy the image with "sudo dd if=arch_linux_mainline.img of=/dev/sdX bs=4M && sync".
Insert the micro SD card into the XU4, connect ethernet, and apply 5V power.
Use SSH to the IP address given to the board by your router.
Login as the default user alarm with the password alarm.
The default root password is root.
Have fun.