If I knew anything non-public (and in this case I don't -- this is from before my time there), I wouldn't be able to talk about it :-)

This has now been pointed out in another thread, but this feature is documented in the datasheet here: http://datasheets.chipdb.org/VIA/Nehemiah/VIA%20C3%20Nehemia.... See Appendix A, A-9 & A-10, as well as the section on CPUID bits.