2Charlie, I don't believe there is any, and especially not in Enterprise. Both editions (Standard and Enterprise) DO in fact have *licensing* limitations, in terms of how many processors are supported to be used, which will depend on edition and number of processors licensed. See the EULA for CF11, and the references there to (and definitions of) cpu's and cores. (And it's changes in most releases, so readers on 10 or 2016 should look at the EULA for those, easily found via googling.
But I don't think there is an actual throttle on number of CPUs used. Care to clarify why you ask? Are you observing something that's suggesting that?
/Charlie (server troubleshooter, carehart.org)