Please be careful here. I have built home computers, using
earlier-generation processors, with clock speeds below 10Mhz.
I've also seen the results of new designs with new processors,
running at speeds above 60Mhz. When you turn one of these puppies
on in a room that's instrumented for EMI (Electro-Magnetic Interference)
detection, the spectrum analyzer goes completely nuts. About the
only way to reduce the EMI is to use extremely sophisticated,
extremely expensive, software tools to model the circuits during
design.
OK, the FCC should not ban these things a priori, but they
should require compliance with FCC class B EMI regulations.
Otherwise, you could kill the guy with the pacemaker in the
next apartment.