From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Fri, 21 Mar 2003 00:43:28 +0000 Subject: Re: [Linux-ia64] provide /proc/sal/itc_drift through AUX? Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Thu, 20 Mar 2003 15:55:02 -0800, Rich Altmaier said: Rich> Jes, regarding your query on real life ITC drifts, I have this Rich> input. Typical crystals used for the CPU clock today have an Rich> accuracy of 250ppm. That is 250 parts per million. Which Rich> means for each million ticks, it may actually be 250 realtime Rich> units too fast or too slow. So in one second's worth of 1GHz Rich> ticks, it may be wrong versus realtime by 250 microseconds. Rich> (not to belabor the point, but then a 1 millisecond error Rich> accumulates each 4 seconds). Good point. Rich> In case you ask "how can this be, my digital watch is better Rich> than that". Your watch is better designed, plus it has more Rich> temperature stability on your arm. Plus nobody is willing to Rich> buy expensive crystals for the computer... Well, most watches don't run at 1GHz either! ;-) --david