What does the Spread Spectrum option in the BIOS do?

[xagent]

I understand what spread spectrum means from an electrical engineering POV, but in my BIOS I have two options for Spread spectrum.

One is in the Frequency/Voltage Control menu, another is in some other menu option and called SB600 (I have an ati xpress 3200 chipset) Spread spectrum. What exactly do they do? Should I have them enabled or disabled? Does it affect performance? stability?

[SomeoneWhoIsntMe]

Spread Spectrum Control: This function is used for meeting the specifications when complying with the CE acceptance test. Enabling it leads to a noticeable deterioration in performance. That's why it should always be disabled!

http://www.tomshardware.com/2001/07/...ng/page18.html

edit

When the motherboard clock generator pulses, the extreme values (spikes) of the pulses creates EMI (Electromagnetic Interference).
The "Spread Spectrum" function reduses 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 problem, leave the setting at "Disable" for optimal system stability and performce. But if you are plagued by EMI, set to "Enable" for EMI reduction.
Remember to disable "Spread Sprectrum" if you are overclocking because even the slight jitter can introduce a temporary boost in clock speed which may just cause your overclocked processor to lock up.

http://forums.amd.com/index.php?showtopic=46026

[wwilliam54]

it varies the FSB by a small amount constantly to help in high interference situation

edit:http://en.wikipedia.org/wiki/Spread_...nal_generation
edit 2: if you have a shit ton of boards side by side, it would not be a bad thing to use