🚀 go-pugleaf

> In article <1992Dec16.011918.25341@eng.ufl.edu>, iqbal@omaha.eel.ufl.edu
> (M.Iqbal) writes: 

> > In article <1992Dec12.003507.1@research.ptt.nl>, walvdrk_r@research.ptt.nl
> >(Kees van der Wal) writes: 

> > |> [about clock frequency to be fed to 486DX2]

> > |> Though I still wonder where my DX2 get's its 66MHz
> > |> clock from if the crystal runs at 33MHz only. Does it contain some
> > |> internal clock doubler circuitry? 

> > Square wave have infinte number of frequencies: a fact explained in 
> > any introductory communication book. If you do not believe me than 
> > try finding Fourier Transform of a pulse train or see a specturm
> > of a pulse train on a spectrum analyzer. 

I believe the book. The book say that symmetric waveforms have no even
harmonics, so the probably symmetric 25 or 33MHz clock has to be converted into
something asymmetric to be useful. 

It would require some kind of filtering to select the second harmonic. As 
having some LC-filtering on-chip doesn't seem very likely, I'm still wondering 
how the 486-designers made it work.

Regards, <kees>