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Date:      Sun, 2 Aug 1998 23:59:55 -0500
From:      Dan Nelson <dnelson@emsphone.com>
To:        "Henry; Michael Kenneth" <mhenry@white.ug.cs.usyd.edu.au>, freebsd-questions@FreeBSD.ORG
Subject:   Re: Processor
Message-ID:  <19980802235955.A3493@emsphone.com>
In-Reply-To: <199808030250.TAA15503@hub.freebsd.org>; from "Henry; Michael Kenneth" on Mon Aug  3 12:50:24 GMT 1998
References:  <199808030250.TAA15503@hub.freebsd.org>

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In the last episode (Aug 03), Henry; Michael Kenneth said:
> I am preparing to make my own kernel, but I have a question about
> the processor options.
> 
> The GENERIC config file has options for 386, 486, 586, and 686 processors.
> 
> I am using a Cyrix 6x86MX, and therefore the 686 option seems to make
> the most sense, but the LINT config file says the 586 is for Pentium
> processors and the 686 is for Pentium Pro processors.
> 
> I am unsure which option to choose, and would appreciate it if someone
> could give me a clue.

"dmesg | grep ^CPU" will do the trick:

(machine1) CPU: i486 DX2 (486-class CPU)
(machine2) CPU: AMD Am5x86 Write-Through (486-class CPU)
(machine3) CPU: Pentium/P54C (132.61-MHz 586-class CPU)
(machine4) CPU: Pentium II (quarter-micron) (398.29-MHz 686-class CPU)

Note that on machine 2, an AMD 5x86 really only supports 486
instructions.  According to identcpu.c, a "Cyrix 6x86" is a souped-up
486, but a "Cyrix 6x86MX" supports 686 instructions.

Looking at the kernel source though, I doubt you'll get much of a
performance increase by commenting out unneeded cputypes.  Just leave
486, 586, and 686 in, and you won't have to worry about recompiling
your kernel if you swap CPUs.

	-Dan Nelson
	dnelson@emsphone.com

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