From owner-freebsd-questions@FreeBSD.ORG  Fri Oct 14 20:07:34 2005
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
X-Original-To: freebsd-questions@freebsd.org
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 61A8716A41F
	for <freebsd-questions@freebsd.org>;
	Fri, 14 Oct 2005 20:07:34 +0000 (GMT) (envelope-from pb@ludd.ltu.se)
Received: from mother.ludd.ltu.se (mother.ludd.ltu.se [130.240.16.3])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 9531243D68
	for <freebsd-questions@freebsd.org>;
	Fri, 14 Oct 2005 20:07:32 +0000 (GMT) (envelope-from pb@ludd.ltu.se)
Received: from brother.ludd.ltu.se (brother.ludd.ltu.se [130.240.16.78])
	by mother.ludd.ltu.se (8.12.10+Sun/8.12.10) with ESMTP id
	j9EK7UGc024898; Fri, 14 Oct 2005 22:07:30 +0200 (MEST)
Received: from brother.ludd.ltu.se (localhost [127.0.0.1])
	by brother.ludd.ltu.se (8.12.10+Sun/8.12.2) with ESMTP id
	j9EK7UCZ011716; Fri, 14 Oct 2005 22:07:30 +0200 (MEST)
Received: (from pb@localhost)
	by brother.ludd.ltu.se (8.12.10+Sun/8.12.2/Submit) id j9EK7TI6011714;
	Fri, 14 Oct 2005 22:07:29 +0200 (MEST)
From: Peter B <pb@ludd.ltu.se>
Message-Id: <200510142007.j9EK7TI6011714@brother.ludd.ltu.se>
To: bkoenig@cs.tu-berlin.de (=?ISO-8859-1?Q?Bj=F6rn_K=F6nig?=)
Date: Fri, 14 Oct 2005 22:07:29 +0200 (MEST)
In-Reply-To: <4350832B.5020600@cs.tu-berlin.de> from
	"=?ISO-8859-1?Q?Bj=F6rn_K=F6nig?=" at Oct 14, 2005 09:18:51 PM
X-Mailer: ELM [version 2.5 PL6]
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit
Cc: freebsd-questions@freebsd.org
Subject: Re: TSC Timer "Quality" ?
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 14 Oct 2005 20:07:34 -0000

>
>Intel pentium cpu timer tsc:
>  'Timecounter "TSC" frequency X Hz quality Y' (from dmesg)
>
>What is the definition of "quality" ..?
>
>
>I have looked briefly in the /usr/src/sys/i386/i386/tsc.c sourcefile and
>the intel-celeron datasheet. Without finding anything useful.
>
>   From src/sys/sys/timetc.h:
>        54         int                     tc_quality;
>        55                 /*
>        56                  * Used to determine if this timecounter is
>   better than
>        57                  * another timecounter higher means better.
>   Negative
>        58                  * means "only use at explicit request".
>        59                  */
>   As far as I understand this, it is used internally only.
>   Regards
>   Björn

Hmm.. should have looked into the header =)
Guess I'll have to check the clock circuit physicaly..

The reason for asking is to explore a way to sample signals asynchronously.
But useing timestamps to calculate how it looks when sampled synchronously.
Thus avoiding the need for fifo circuitry.


Btw, avoid html encoded email pls.