*BSD News Article 87719


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From: kato@eclogite.eps.nagoya-u.ac.jp (KATO Takenori)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Cyrix P166+ CPU patch - is it available?
Date: 28 Jan 1997 17:23:29 GMT
Organization: Nagoya University Computation Center
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References: <5bmvnp$5dj@hermes.acs.unt.edu>
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In article <5bmvnp$5dj@hermes.acs.unt.edu>
	jackson@replicant.csci.unt.edu (Bruce Jackson) wrote:

> For the jobs I run there is little floating point math.  For me a
> Cyrix CPU was both cheaper and faster than a Pentium.  Under FreeBSD
> it does probe as a '486 but it still performs great.  I built a kernel
> that would identify the CPU as a Pentium class CPU but it crashed
> while booting with a supervisor violation.  Perhaps in the future
> FreeBSD will better support the 6x86 CPU's but for the time being it
> does seem like a good choice to me.

Cyrix 6x86 is a 486-class CPU.  It supports the 486 instruction set,
but it doesn't support the Pentium extensions for virtual mode,
internal counters and additional debug capability.

If the variable cpu_class is Pentium, kernel executes wrmsr and rdtsc
instructions, which is not supported, then crash.


----
KATO Takenori <kato@eclogite.eps.nagoya-u.ac.jp>
Dept. Earth Planet. Sci., Nagoya Univ.,  Nagoya, 464-01, Japan