From owner-freebsd-bugs  Fri Mar 12 19:30:19 1999
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Date: Sat, 13 Mar 1999 05:23:12 +0200 (EET)
From: Juha Nurmela <junki@qn-lpr2-98.quicknet.inet.fi>
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To: FreeBSD-gnats-submit@freebsd.org
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Subject: kern/10565: Slow timekeeping on certain motherboards/cpus/chipsets
Sender: owner-freebsd-bugs@FreeBSD.ORG
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>Number:         10565
>Category:       kern
>Synopsis:       Slow timekeeping on certain motherboards/cpus/chipsets
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Fri Mar 12 19:30:00 PST 1999
>Closed-Date:
>Last-Modified:
>Originator:     Juha Nurmela
>Release:        FreeBSD 4.0-CURRENT i386
>Organization:
ACME Inc.
>Environment:

	Timecounter "i8254"  frequency 1193182 Hz
	Timecounter "TSC"  frequency 74539244 Hz
	CPU: AMD K5 model 0 (74.54-MHz 586-class CPU)
		Origin = "AuthenticAMD"  Id = 0x500  Stepping=0
		Features=0x3bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8,APIC>

	chip0: <Intel 82437VX PCI cache memory controller> rev 0x02 on pci0.0.0
	chip1: <Intel 82371SB PCI to ISA bridge> rev 0x01 on pci0.7.0

>Description:

	Time does not increment. Well, very slowly and not in any determinable
	constant rate. Using the timerchip for timecounter instead
	of tsc register works around the problem.

	Another 'fix' with my mobo is to keep the cpu busy, and not let
	it enter HLT. 'while : ; do date; done' almost does the trick as
	well as a idle-priority process in tight loop (does it better).

	Looks like the mobo does bad SMI stuff whenever a HLT is executed,
	and it cannot really be changed in the bios settings which disable
	power management.

>How-To-Repeat:

	With this kind of PC, build a kernel which contains no apm0,
	nor SMP, and watch date in idlish system, then in busyish system.
	Date should step almost properly in busy state and halt
	almost completely in idle system.

>Fix:

	It might be nice to have a std way to set the existing hlt_vector in
	swtch.s into just RET (which it already is with SMP).
		options "CPU_HALT_NO" and/or
		sysctl -w machdep.do_halt=0
	cp_time[] via sysctl would be nice too...


>Release-Note:
>Audit-Trail:
>Unformatted:


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