X48 Rampage Formula Preview.

[Brama]

CPU / PCI-E spread spectrum.
According to what I've read from Intel docs, these basically take a mean frequency across associated clock frequencies and use as reference for. I personally disable both as they affect RTC/PCI-E/CPU address/CPU data clocks which can make an OC very unstable.

This is not well explained
Normally the clocks are pure single frequency signals with very low sideband noise.
On a spectrum scope they appear as a vertical line very thin and clean. As on spectrum scopes monitor the X-axis represents frequency and the Y-axis signal's voltage, a very high and clean vertical line means a clean and powerfull clock signal on a single frequency.

This is the best clock that enables the digital components to work at their best.

Unfortunately this very clean and high signal could overcome the limits written in FCC and EC rules about EMC. If this occurs, the system can not obtain the FCC/EC mark and can not be sold.

As these rules measure the EMC level with a quasi-peak filter, it is better to use a clock not so clean. In the spectrum scope it will be no more a vertical line, but a very thin gaussian curve. It means that all the energy of clock is not on one frequency, but is spread a little around the central frequency of signal.

This is very easily done by modulating in frequency the clock signal.

This trick fools the quasi-peak detector of receiver used to test the EMC and, even if not perfect, allows the normal working of the device.

As in normal offices or houses environments the EMC is not so important, it is better to disable the spread spectrum of clocks to have the best performances in overclock.

I hope I have explained a little this difficult argument