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Date: Wed, 1 Jun 2011 14:46:22 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
To: Adam Vande More <amvandemore@gmail.com>
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	(wonkity.com [127.0.0.1]); Wed, 01 Jun 2011 14:46:22 -0600 (MDT)
Cc: questions@freebsd.org
Subject: Re: I486_CPU or I586_CPU in kernel config
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On Mon, 30 May 2011, Warren Block wrote:

> On Mon, 30 May 2011, Adam Vande More wrote:
>
>> Perhaps this is the one you meant?
>> 
>> http://lists.freebsd.org/pipermail/freebsd-questions/2009-January/190568.html
>
> That's the one!  Thanks!
>
>> Actually the two threads touch on the same subject, and it seems removal of 
>> those options is still desirable on newer CPU's.
>
> sys/i386/i386/support.s is mentioned, but doesn't seem to have anything 
> explicitly specific for 586.  There are some i686 entries.
>
> A test for cpu_class==CPUCLASS_586 in /sys/i386/isa/npx.c is mentioned in the 
> thread, but that check isn't in the current code.

A little empirical testing:

Times for buildworld after a fresh reboot, /usr/obj/usr deleted, 
GENERIC included, running ccache:

default (486/586 included)	9:05.84
nocpu I486, nocpu I586_CPU	9.27.88
nocpu I486_CPU			8.53.86

So maybe a 6% increase by removing 486 but leaving 586...  These were 
not rigorous benchmarks, it might just be measurement noise.