From kmartinez@utexas.edu Sun Jan 21 23:15:12 1996
Path: ashpoly!bigsur!pacrim!krgate!eunha!utexas!kmartinez
From: kmartinez@utexas.edu (Katrin Martínez)
Newsgroups: comp.dsp
Subject: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Jan21.231512.7257@utexas.edu>
Date: Sun, 21 Jan 1996 23:15:12 GMT
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Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.

This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks.
By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample.

Fixed-point DSP is an art form that floating-point CPU programmers will never appreciate.

-- 
Katrin Martínez | kmartinez@utexas.edu
PGP Key fingerprint: F0B2 0A69 328E C758
"Keep the channels open."

From avasiliev@panix.com Mon Jan 22 04:01:12 1996
Path: ashpoly!cascade!brgate!saturno!panix!avasiliev
From: avasiliev@panix.com (Astrid Vasiliev)
Newsgroups: comp.dsp
Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Jan22.040112.6104@panix.com>
Date: Mon, 22 Jan 1996 04:01:12 GMT
References: <1996Jan21.231512.7257@utexas.edu>
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In article <1996Jan21.231512.7257@utexas.edu>, kmartinez@utexas.edu (Katrin Martínez) writes:
> Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.
> This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks.

Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in.

-- 
Astrid Vasiliev | avasiliev@panix.com
PGP Key fingerprint: 3444 57F5 6D9E EEE5
"Keep the channels open."