At about the 35 minute mark of this fascinating and witty talk by Paul Horowitz - one of the co-authors of “The Art of Electronics” there’s a short bit about the suitcase-portable SETI kit which uses a 68000 powered WICAT WS150 and a dual 68000 FFT appliance.

There was a WICAT still running in production in 2010.

Also in this talk some hints on the history of the FFT algorithm. Which led me to this paper

Cooley, J. W. (1987). *The re-discovery of the fast Fourier transform algorithm. Mikrochimica Acta, 93(1-6), 33–45.* doi:10.1007/bf01201681

Even with this nice inversion property, when the number of terms in the series and the number of x’s is N, the number of operations is N^2. The FFT algorithms which I am talking about here reduce this to N log(N), a speed-up of a factor of N/log (N). Modest sized sample records start at around N=1000 meaning a speed-up factor of 100. The spectrometry calculation I will mention later had N=512000 meaning that if one even considered the calculation by a direct method, the speed-up factor would be about 12800.

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Howard Smith, a member of the APL group, put the algorithm in APL when it was only a language for defining processes and before it was implemented on any machine. This gave the algorithm a thorough working over at the other seminars.