How many CPU cores does FreeBSD support?

[Shane Ambler]

On 04/01/2017 08:08, Eric Joyner wrote:
> 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?

You will probably find freebsd-current a better mailing list for this.

How many show in dmesg?

 From https://svnweb.freebsd.org/base?view=revision&revision=270223
Bump MAXCPU on amd64 from 64 to 256.  In practice APIC only permits 255
CPUs (IDs 0 through 254).  Getting above that limit requires x2APIC.

Also note that changing MAXCPU breaks ABI compatability so you will
need to recompile.
https://svnweb.freebsd.org/base?view=revision&revision=284720

-- 
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Shane Ambler