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Date: Sat, 9 Aug 1997 13:29:52 -0600 (MDT)
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Subject: kern/4255: SMP kernel freezes on machines with >2 CPUs.
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>Number:         4255
>Category:       kern
>Synopsis:       SMP kernel freezes on machines with >2 CPUs.
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Aug  9 12:40:01 PDT 1997
>Last-Modified:
>Originator:     Steve Passe
>Organization:
Steve's Cafe
>Release:        FreeBSD 3.0-CURRENT i386
>Environment:

	SMP kernel on machines with >2 CPUs.

>Description:

	When the kernel config file "options NCPU=x" line has a value for x
	that doesn't agree with the actual number of CPUs on the motherboard
	the kernel will usually freeze during boot.

>How-To-Repeat:

	set "options NCPU=x" to 2 on a board with 4 CPUs.

>Fix:
	
	For now just make sure that "options NCPU=x" agrees with the actual
	CPU count of your motherboard.  The default is NCPU=2, so most
	users needn't bother.  Those with hardware containing 4 CPUs
	will have to make sure to add "options NCPU=4" to their config
	files for now.

	The correct fix is to examine mpboot.s and determine why the
	additional CPUs get into the race for the bootlock (my current
	theory as to the cause of the problem).


>Audit-Trail:
>Unformatted: