RE: Spread Spectrum PCI clock

["Ingraham, Andrew" <Andrew.Ingraham@compaq.com>]

The PCI revision 2.2 spec does address SSC, but only for 66MHz operation.
For 33MHz PCI, SSC is unlimited.  The reason being, that the 33MHz clock has
always been allowed to change frequency at any time, skip cycles, and even
fully stop.

No PLL in the world can track that.

Which is why a PLL should never be used on a marketable PCI card designed
for the 33MHz PCI spec.  Sorry.

By definition, the SSC on a 33MHz motherboard is unlimited, in both
modulation rate and deviation (except that the period should never be less
than 30ns).

Andy