From asanchez@stanford.edu Wed Dec 06 10:48:42 1995
Path: ashpoly!cascade!bigsur!stanford!asanchez
From: asanchez@stanford.edu (Astrid Sánchez)
Newsgroups: comp.dsp
Subject: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Dec06.104842.6427@stanford.edu>
Date: Wed, 06 Dec 1995 10:48:42 GMT
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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.
The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead.

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

-- 
Astrid Sánchez | asanchez@stanford.edu
PGP Key fingerprint: 7A0C 083E 54D0 7E99
"Keep the channels open."

From glopez@uu.net Thu Dec 07 11:45:42 1995
Path: ashpoly!bigsur!pacrim!jpgate!kamome!uu!glopez
From: glopez@uu.net (Göran López)
Newsgroups: comp.dsp
Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Dec07.114542.2542@uu.net>
Date: Thu, 07 Dec 1995 11:45:42 GMT
References: <1995Dec06.104842.6427@stanford.edu>
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In article <1995Dec06.104842.6427@stanford.edu>, asanchez@stanford.edu (Astrid Sánchez) writes:
> Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip.

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

-- 
Göran López -- UUNET Technologies, Falls Church VA
"We don't sign stars. We build them."