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Date: Mon, 14 Apr 1997 21:45:58 +0100
From: Bob Bishop <rb@gid.co.uk>
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To: FreeBSD-gnats-submit@freebsd.org
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Subject: kern/3292: Cyrix 486 performance problem
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>Number:         3292
>Category:       kern
>Synopsis:       Cyrix 486 performance problem
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Apr 14 14:10:01 PDT 1997
>Last-Modified:
>Originator:     Bob Bishop
>Organization:
GID ltd
>Release:        FreeBSD 3.0-CURRENT i386
>Environment:

	Cyrix 486DX2/80, ISA M/B, 20Mb, Adaptec1542CF

>Description:

	With kernels built after around 20 March, CPU runs an
	order of magnitude slower than it should. Eg, kernel
	build takes 3.25 hours against 28 min; tiny program
	containing nested for loops takes 51 sec against 4
	sec.

	Old (ie good) kernels identify the CPU as:
		CPU: Cy486DLC (486-class CPU)
		   Origin = "Cyrix"
	Newer (broken) kernels:
		CPU: Cyrix 486DX2 (486-class CPU)
		   Origin = "CyrixInstead"  Device ID = 0x321b
		    Stepping=3  Revision=2

	I surmise that the CPU initialisation code got broken
	sometime around 20 March.

>How-To-Repeat:

	Run anything on this machine with a current-ish
	kernel.

>Fix:
	
	Work around by using an old kernel :-(

>Audit-Trail:
>Unformatted: