Re: [PATCH] x86: Export tsc related information in sysfs

[H. Peter Anvin]

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.)

	-hpa
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