I recently got my apu1d board, but I have problems booting TinyCore Linux on it. Here are the steps I follow
1) Under Mac OS X, Disk Utility application I formatted a USB stick to MS-DOS FAT.
2) I downloaded TinyCore from http://pcengines.ch/file/apu_tinycore.tar.bz2, extracted it and moved the files to the USB stick
3) I powered up the apu1d, opened a serial conenction from an OpenBSD laptop to it and configured it to boot from USB1
4) I plugged to USB stick to the apu1d and restarted it. I got the follwoing messages from the serial console:
$ sudo cu -s 115200