There are so many threads about which HW platform might be a candidate for this "ambitious project" that we may have already discussed the answer.
I haven't read them all, but as Tension says "brace yourselves for disappointment".
Taking into account that x86 has been ruled out, I decided to Google PPC on x86 and a number of PPC PCI/PCIe processor board hits were returned.
Does anyone here have an informed opinion as to whether this would be a viable option for getting OS onto "mainstream HW"?
