Date: Mon, 28 Jan 2008 10:53:21 -0800 From: Sean Bruno <sbruno@miralink.com> To: Jason Slagle <raistlin@tacorp.net> Cc: freebsd-hackers@freebsd.org Subject: Re: How long is a hz? Message-ID: <479E24A1.60103@miralink.com> In-Reply-To: <20080128134253.C1539@mail.tacorp.net> References: <479E0A1C.2060908@miralink.com> <20080128134253.C1539@mail.tacorp.net>
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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
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