From owner-freebsd-hackers@FreeBSD.ORG Mon Jan 28 18:53:25 2008 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 7F70816A418 for ; Mon, 28 Jan 2008 18:53:25 +0000 (UTC) (envelope-from sbruno@miralink.com) Received: from plato.miralink.com (mail.miralink.com [70.103.185.20]) by mx1.freebsd.org (Postfix) with ESMTP id 5BE6513C4CE for ; Mon, 28 Jan 2008 18:53:25 +0000 (UTC) (envelope-from sbruno@miralink.com) Received: from localhost (localhost.localdomain [127.0.0.1]) by plato.miralink.com (Postfix) with ESMTP id 285B061B945; Mon, 28 Jan 2008 10:53:23 -0800 (PST) Received: from plato.miralink.com ([127.0.0.1]) by localhost (plato.miralink.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 28312-10; Mon, 28 Jan 2008 10:53:22 -0800 (PST) Received: from [10.47.1.130] (vpn.office.miralink.com [10.0.0.5]) by plato.miralink.com (Postfix) with ESMTP id 164EB61B935; Mon, 28 Jan 2008 10:53:22 -0800 (PST) Message-ID: <479E24A1.60103@miralink.com> Date: Mon, 28 Jan 2008 10:53:21 -0800 From: Sean Bruno User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Jason Slagle References: <479E0A1C.2060908@miralink.com> <20080128134253.C1539@mail.tacorp.net> In-Reply-To: <20080128134253.C1539@mail.tacorp.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-DSPAM-Result: Innocent X-DSPAM-Processed: Mon Jan 28 10:53:22 2008 X-DSPAM-Confidence: 0.9993 X-DSPAM-Probability: 0.0000 X-DSPAM-Signature: 479e24a220291091686056 X-DSPAM-Factors: 27, X-Virus-Scanned: amavisd-new at X-Spam-Status: No, score=-4.499 tagged_above=-10 required=6.6 autolearn=ham tests=[ALL_TRUSTED=-1.8, BAYES_00=-2.599, DSPAM_HAM=-0.1] X-Spam-Score: -4.499 X-Spam-Level: Cc: freebsd-hackers@freebsd.org Subject: Re: How long is a hz? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 28 Jan 2008 18:53:25 -0000 Jason Slagle wrote: > On Mon, 28 Jan 2008, Sean Bruno wrote: > >> I couldn't quite find the definition for "hz" in sys/ this morning. >> What is it's value and where is it defined? > > From http://en.wikipedia.org/wiki/Hertz > > The hertz (symbol: Hz) is the International System of Units (SI) base > unit of frequency. Its base unit is cycle/s or s^-1 (also called > inverse seconds, reciprocal seconds). In English, hertz is used as > both > singular and plural. As any SI unit, Hz can be prefixed; commonly used > multiples are kHz (kilohertz, 10^3 Hz), MHz (megahertz, 10^6 Hz), GHz > (gigahertz, 10^9 Hz) and THz (terahertz, 10^12 Hz). > > One hertz simply means one cycle per second (typically that which is > being counted is a complete cycle); 100 Hz means one hundred cycles > per > second, and so on. The unit may be applied to any periodic event--for > example, a clock might be said to tick at 1 Hz, or a human heart might > be said to beat at 1.2 Hz. The frequencies of aperiodic events, > such as > radioactive decay, are expressed in becquerels. > > But more importantly, where is "hz" defined in the kernel tree? Sean