Robert Elz <kre@munnari.OZ.AU> writes:

> Actually that raises a comparison question ... compiling kernels
> that support all the versions of x86 processors, or sparc processors
> (and probably others where one kernel supports a processor family)
> has a bunch of costs, as the low level code needs to be constantly
> checking which processor is currently being used to select the
> correct code path.

Tim Rightnour did a few tests of i386 GENERIC vs
GENERIC-tuned-for-i686 recently. See the thread starting with this
message:

http://mail-index.netbsd.org/tech-perform/2006/02/02/0026.html

The improvement for using the i686-tuned code was in the 2-5% range.

        - Nathan