Messages in this thread | | | Date | Mon, 24 May 2010 11:19:56 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] x86: Export tsc related information in sysfs |
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On 05/24/2010 11:13 AM, Dan Magenheimer wrote: > Just wondering: If one were to put an ultra-precise scope on > a processor, how far off would the calibrated value be? I'd > imagine the process of calibrating one unknown crystal against > a second crystal which has a known-but-not-highly-precise > frequency, though good enough for most purposes, is not particularly > accurate. In other words, maybe the stamped rate is more accurate > than the calibrated rate anyway?
No. Not even close.
A spread-spectrum clock is inaccurate by entire percentage points. A non-spread clock is typically ±50 ppm with typical consumer PC oscillators, ±1 ppm with non-crappy but still cheap oscillators (e.g. used in cell phones.)
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