FreeBSD 7.1-Stable only support 16 CPUs !?

[Robert Watson]

On Thu, 12 Feb 2009, James Chang wrote:

>    Does any ever try FreeBSD 7.1-stable on box that has more than 16 CPU?
>
> I got a HP ProLiant DL 785 G5 with 32 core (Quad-Core AMD Opteron(tm) 
> Processor 8356 (2300.10-MHz K8-class CPU) and 256G memory. When I boot this 
> machine, it could detect 32 core, but only 16 core could be uesd!?
>
>    What should I do to get FreeBSD 7.1-stable work with 32 core? Or, FreeBSD 
> 7.1 only support 16 Core Max ?

I can't speak to the specific hardware you have, but one known limitation in 
several versions of FreeBSD is that the MAXCPU constant for i386 and amd64 is 
16.  You can redefine it in src/sys/${arch}/include/param.h and recompile your 
kernel to see the full 32 cores.  You may need to recompile some userspace 
tools in order for them to properly report statistics for all CPUs, so a full 
rebuild of world wouldn't hurt.

Robert N M Watson
Computer Laboratory
University of Cambridge