This should get you going with PXE boot on a Mac OS X box:

* Become root and untar this file in your /

* Create a network location called "PXE boot", and set the IP on your
  Ethernet port to 192.168.200.1.

* Enable web sharing.

* Go to http://metrix.net/support/dist/ and download the latest
  Metrix Pebble distribution.  Put it in /Library/Webserver/Documents and
  gzip -d it.  Do *not* untar it.  Rename (or symlink) the tar to 'os'.

* Connect a serial USB dongle to the console port on the Soekris and run
  '/sw/bin/minicom soekris' as root.  Don't forget a null modem adapter 
  if required.

* Connect your Ethernet to the Soekris board (port 0 if you have multiple
  Ethernet ports). Power up the Soekris, and at the BIOS prompt hit Control-P.

* Run /usr/sbin/pxeboot as root.  You must have link on your Ethernet or
  DHCP will not start.  If you don't see DHCP binding to 192.168.200.1,
  check your cabling and try it again.

* On the serial console, type "boot F0".

* When you're done, kill pxe with '/sbin/pxeboot die'

Have fun!

--Rob Flickenger
Metrix Communication LLC
http://metrix.net/