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