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I've seen computers that have a spread spectrum* feature meant to reduce EM emissions. How would this analysis fare against such a machine? My guess is probabl
by whoopdedo 11y ago
I've seen computers that have a spread spectrum* feature meant to reduce EM emissions. How would this analysis fare against such a machine?
My guess is probably not at all. Because I've never seen the option in a notebook computer, and as the purpose is to pass emissions regulation, I assume it was enabled in the machines they tested. And that the difference in the emitted frequencies of various operations is much greater than any variation of the base clock.
[*] http://www.anandtech.com/show/2500/20 http://www.anandtech.com/show/2500/20
- raverbashing 11y agoIIRC what it does is add some (tiny amount of) jitter to the clock signal; what this does is to "flatten" the spectrum of the emitted signal slightly (because instead of having a peak at 1GHz, let's say, it's going to be spread around, but centered on that frequency)
- jloughry 11y agoThe reason the feature exists is so the equipment can pass EMC (electromagnetic compatibility) tests such as FCC Part 15 for emissions. By spreading the radiated energy further out across the frequency domain, the peak amplitude is reduced and you stay under the limit. Of course this raises the noise floor for everyone, but my sheep ought to be able to graze in the common.