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On 2020-03-05, madscientistatlarge <madscientistatlarge@××××××××××.com> wrote: |
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> To reduce problems with emitted Radio Frequency Interference, most |
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> processors now use a clock that varies in speed over time. This |
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> doesn't really reduce the emitted energy, but because it is always |
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> changing frequency interference with other devices tends to be |
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> intermittent, and Ideally unnoticeable. Also the oscillators used |
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> in computers are not the most precise, they don't need to be and |
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> precision cost. The bios may let you toggle this deliberate |
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> frequency variation and off, which I suppose could be critical in |
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> some real-time cases, or a varying clock may, in some cases cause |
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> objectionable interference where as the fixed clock, may not, YMMV. |
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A clock that varies like that is usually referred to has a |
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"spread-spectrum" clock. If properly implimented it has no measurable |
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effect on software execution (even for real-time cases) because the |
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variation is done so that the average frequency is "constant" and the |
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deviation from that average sums to 0 for any significant period of |
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time (anything over a few hundred microseconds). |
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The variation of the average over temperature and supply voltage is |
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usually far more significant. |
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-- |
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Grant Edwards grant.b.edwards Yow! PIZZA!! |
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at |
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gmail.com |