Messages in this thread |  | | Date | Fri, 28 Sep 2001 23:24:58 +0100 | From | Jamie Lokier <> | Subject | Re: CPU frequency shifting "problems" |
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Eric W. Biederman wrote: > > What does exist is the bus clock (well, a multiple of it, but you get the > > idea), and that one is stable. I bet PCI devices don't like to be randomly > > driven at frequencies "somewhere between 12 and 33MHz" depending on load ;) > > I doubt they would like it but it is perfectly legal (PCI spec..) to > vary the pci clock, depending upon load.
Yes it is. Also, the PCI clock is frequency modulated to reduce electrical interference. (Or on a more cynical note, to pass the official emissions tests ;-)
However it's common practice to PLL to the PCI clock, for clock distribution on a board, so varying the frequency must be done in a strictly constrained fashion.
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