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To: Pierre.Beyssac@hsc.fr
Cc: freebsd-security@freebsd.org
Subject: Re: now a Cyrix processor bug
From: KATO Takenori <kato@migmatite.eps.nagoya-u.ac.jp>
In-Reply-To: Your message of "Tue, 18 Nov 1997 10:54:17 +0100"
References: <19971118105417.FC32400@mars.hsc.fr>
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Date: Tue, 18 Nov 1997 19:30:17 +0900
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> Has anynone seen this?
> 
> There seems to be a bug on the Cyrix, similar but not identical
> to the Pentium's. However the workaround on the Cyrix is apparently
> much simpler (you only need to disable LOCK mode in the CCR, if I
> understood the fix right).

3.0-current and RELENG_2_2 (including 2.2.5) have following option:

	CPU_CYRIX_NO_LOCK

which enables weak locking.  Because I didn't know of the Coma bug,
and recomended setting of NO_LOCK bit is 0 in the BIOS writer's guide, 
NO_LOCK bit is not modified when above option is not set.  Because SMP 
of FreeBSD doesn't support non-Intel chipsets, CPU_CYRIX_NO_LOCK
options may have no harmful effect.

Also, another fix via special registers is propsed.  But, Cyrix
doesn't disclose the meanings of such registers.  When Cyrix discloses 
the meaning of registers, I will implement latter fix.

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