VIA Technologies P4PB ULTRA-URL User Manual page 65

BIOS Setup
Spread Spectrum
When the mainboard's clock generator pulses, the extreme values (spikes) of the
pulses creates EMI (Electromagnetic Interference). The Spread Spectrum func-
tion reduces the EMI generated by modulating the pulses so that the spikes of the
pulses are reduced to flatter curves. If you do not have any EMI problems, leave
the setting at Disabled for optimal system stability and performance. But if you
are plagued by EMI, setting to Enabled for EMI reduction. Remember to disable
Spread Spectrum if you are overclocking because even a 0.25% jitter can intro-
duce a temporary boost in clock speed of 25MHz (with a 1GHz CPU) which
may just cause your overclocked processor to lock up. Settings: Disabled, +/-0.
25%, -0.5%, +/-0.5% and +/-0.38%.
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