Some "simple" methods to hack the SMP86xx based boards, even XPU I would assume.
http://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-630.html (http://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-630.html)
As susual every protection can be defeated - as long as you have unlimited time, money, or just the right tools for the job. Unfortunately I have neither...