From mito@cmu.edu Thu Oct 12 01:12:21 1995
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From: mito@cmu.edu (Mei Ito)
Newsgroups: comp.dsp
Subject: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Oct12.011221.3931@cmu.edu>
Date: Thu, 12 Oct 1995 01:12:21 GMT
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Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.

The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead.
This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks.

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

-- 
Mei Ito | mito@cmu.edu
PGP Key fingerprint: F8DD 96DF 6A7B 871E
"Keep the channels open."

From msmirnov@hanse.de Fri Oct 13 05:53:21 1995
Path: ashpoly!cascade!transat!eunet-fr!teletel!hanse!msmirnov
From: msmirnov@hanse.de (Mathieu Smirnov)
Newsgroups: comp.dsp
Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Oct13.055321.6045@hanse.de>
Date: Fri, 13 Oct 1995 05:53:21 GMT
References: <1995Oct12.011221.3931@cmu.edu>
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In article <1995Oct12.011221.3931@cmu.edu>, mito@cmu.edu (Mei Ito) writes:
> Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.

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

-- 
Mathieu Smirnov
Opinions expressed are solely my own and not those of Hanse-Netzwerk Hamburg.
------------------------------------------------------------

From egirard@cam.ac.uk Fri Oct 13 08:45:21 1995
Path: ashpoly!bigsur!pacrim!krgate!eunha!cam!egirard
From: egirard@cam.ac.uk (Emi Girard)
Newsgroups: comp.dsp
Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Oct13.084521.1271@cam.ac.uk>
Date: Fri, 13 Oct 1995 08:45:21 GMT
References: <1995Oct12.011221.3931@cmu.edu> <1995Oct13.055321.6045@hanse.de>
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In article <1995Oct13.055321.6045@hanse.de>, msmirnov@hanse.de (Mathieu Smirnov) writes:
> Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in.

Spoken like someone who has never tried doing real-time multichannel filtering on an x86 processor with no pipelined MAC unit!

-- 
Emi Girard
Tape trading list upon request. SASE required for international mail.

From jduarte@cern.ch Sun Oct 15 08:31:21 1995
Path: ashpoly!cascade!mxgate!coyoacan!cern!jduarte
From: jduarte@cern.ch (Ji-woo Duarte)
Newsgroups: comp.dsp
Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Oct15.083121.8333@cern.ch>
Date: Sun, 15 Oct 1995 08:31:21 GMT
References: <1995Oct12.011221.3931@cmu.edu> <1995Oct13.055321.6045@hanse.de>
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In article <1995Oct13.055321.6045@hanse.de>, msmirnov@hanse.de (Mathieu Smirnov) writes:
> Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in.

Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering.

-- 
=== Ji-woo Duarte ===
Dept of Electrical Engineering, European Laboratory for Particle Physics, Geneva
"Measuring a record you own is listening, not piracy."