From: David Mosberger <davidm@napali.hpl.hp.com>
To: linux-ia64@vger.kernel.org
Subject: Re: [Linux-ia64] provide /proc/sal/itc_drift through AUX?
Date: Fri, 21 Mar 2003 00:43:28 +0000 [thread overview]
Message-ID: <marc-linux-ia64-105590723705281@msgid-missing> (raw)
In-Reply-To: <marc-linux-ia64-105590723705273@msgid-missing>
>>>>> On Thu, 20 Mar 2003 15:55:02 -0800, Rich Altmaier <richa@engr.sgi.com> 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
next prev parent reply other threads:[~2003-03-21 0:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-03-19 21:39 [Linux-ia64] provide /proc/sal/itc_drift through AUX? Jes Sorensen
2003-03-19 23:54 ` David Mosberger
2003-03-20 2:06 ` Jes Sorensen
2003-03-20 19:57 ` David Mosberger
2003-03-20 23:55 ` Rich Altmaier
2003-03-21 0:43 ` David Mosberger [this message]
2003-03-21 2:04 ` Jes Sorensen
2003-03-21 17:49 ` Jes Sorensen
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