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Date: Wed, 14 Dec 2005 19:06:05 -0500
From: Jonathan Noack <noackjr@alumni.rice.edu>
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To: Scott Long <scottl@samsco.org>
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Cc: stable@freebsd.org
Subject: Re: Odd performance problems after upgrade from 4.11 to 6.0-Stable
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Scott Long wrote:
> Also, taking out CPU_I586 is usually a bad idea.  It offers no 
> performance penalties (unlike CPU_I386 and maybe CPU_I486), but
> enables things like optimized bcopy.

Is that documented?  In /sys/i386/conf/NOTES I see:

# You must specify at least one CPU (the one you intend to run on);
# deleting the specification for CPUs you don't need to use may make
# parts of the system run faster.
#
cpu             I486_CPU
cpu             I586_CPU                # aka Pentium(tm)
cpu             I686_CPU                # aka Pentium Pro(tm)

I've always commented out I486_CPU and I586_CPU.  Shouldn't leaving in 
I686_CPU enable all the features it can use?  Do you mean I've spent all 
these years using un-optimized bcopy?!?

-Jonathan