How many CPU cores does FreeBSD support?

[Eric Joyner]

I have an 11.0-RELEASE-p1 system with:

hw.model: Intel(R) Xeon Phi(TM) CPU 7250 @ 1.40GHz

It's got 68 cores, but with 4-way SMT, I think it should show up with 272
logical cores on FreeBSD.

However, in both kern.sched.topology_spec and hw.ncpu, it shows there are
only 223 cores.

Is the limit effectively 223 cores, even though I see some #define MAXCPU
256 lines in the source?

- Eric