From epark@berkeley.edu Wed Dec 21 20:36:43 1994
Path: ashpoly!bigsur!pacrim!jpgate!kamome!berkeley!epark
From: epark@berkeley.edu (Élodie Park)
Newsgroups: comp.dsp
Subject: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994Dec21.203643.3794@berkeley.edu>
Date: Wed, 21 Dec 1994 20:36:43 GMT
Organization: UC Berkeley Department of EECS
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Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.

However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop.
By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample.

Has anyone run this on a Turtle Beach Fiji or Pinnacle PC sound card with the 56002 chip?

-- 
=== Élodie Park ===
Dept of Electrical Engineering, UC Berkeley Department of EECS
"Hardware is temporary. The signal survives."

From tjohansson@ox.ac.uk Fri Dec 23 16:38:43 1994
Path: ashpoly!cascade!transat!eunet-fr!teletel!ox!tjohansson
From: tjohansson@ox.ac.uk (Thiago Johansson)
Newsgroups: comp.dsp
Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994Dec23.163843.5989@ox.ac.uk>
Date: Fri, 23 Dec 1994 16:38:43 GMT
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In article <1994Dec21.203643.3794@berkeley.edu>, epark@berkeley.edu (Élodie Park) writes:
> Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.

Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete.

PGP Public key available via finger or upon request.

-- 
=== Thiago Johansson ===
Dept of Electrical Engineering, Oxford University Computing Laboratory
"A soul is not exclusive to biology."

From bnovak@uni-hamburg.de Sat Dec 24 11:33:43 1994
Path: ashpoly!cascade!bigsur!uni-hamburg!bnovak
From: bnovak@uni-hamburg.de (Bruno Novak)
Newsgroups: comp.dsp
Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994Dec24.113343.1877@uni-hamburg.de>
Date: Sat, 24 Dec 1994 11:33:43 GMT
References: <1994Dec21.203643.3794@berkeley.edu> <1994Dec23.163843.5989@ox.ac.uk>
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In article <1994Dec23.163843.5989@ox.ac.uk>, tjohansson@ox.ac.uk (Thiago Johansson) writes:
> Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete.

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

Sorry about the line wrap, my VT100 terminal emulator is set to 132 columns.

-- 
Bruno Novak | bnovak@uni-hamburg.de
PGP Key fingerprint: DE75 9BCF 78CE F2A0
"Keep the channels open."