[ntp:questions] Re: drifting on crystal

Brad Knowles brad at stop.mail-abuse.org
Thu Jan 13 08:42:49 UTC 2005

At 6:33 AM +0000 2005-01-13, Marc Brett wrote:

>  That's the hardware cost.  How many watts does it consume?

	No more than the low-quality oscillator that is actually included 
by the hardware vendor.

>                   why would an engineer include a component with "oven" in its
>  name if he didn't have to?

	There is no actual oven included with the crystal.  The issue is 
that the OXCO has gone through a more rigorous testing process which 
includes testing in an oven, and has been certified to work to 
certain tighter performance standards than your average everyday 
crystal, and either actively compensates for temperature variations 
or is relatively immune to them.

	When CPUs are made, at first no one knows how fast a given chip 
will run.  It has to be tested first.  Ones that are stable up to a 
slower speed are sold at a lower price, while ones that are stable to 
higher speeds will be sold for higher prices -- even if they were 
made from the same block of silicon, and in fact were sitting right 
next to each other when the masks were being laid down.

	Same deal for crystal oscillators.  Those that pass the more 
stringent tests are sold for more money, those that don't are sold 
for less.  But other than the passing of the tests (or failure to 
pass), there are no human-discernible differences between the two 
components.  One will get painted a different color than the other, 
so that the manufacturer can tell the difference between them, and 
know which one to sell for which price.

>                             Also, how many people really need that level of
>  accuracy?

	Many people could benefit from it.  Indeed, most everyone who 
uses a computer could benefit from having a better clock, even if 
they don't know it.

>          If hundreds of millions of PCs are consuming watts they don't need,
>  that's wasteful on a pretty grand scale.

	There's no waste of power here.  There is short-sightedness on 
the part of the PC manufacturers, and a willingness to cut off their 
nose to spite their face.  That's all.

Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.

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