From hhughes@cam.ac.uk Wed May 17 10:37:11 1995
Path: ashpoly!cascade!bigsur!cam!hhughes
From: hhughes@cam.ac.uk (Heather Hughes)
Newsgroups: comp.dsp
Subject: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995May17.103711.7353@cam.ac.uk>
Date: Wed, 17 May 1995 10:37:11 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.
However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop.

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

-- 
Heather Hughes -- University of Cambridge Computer Laboratory
"Tape doesn't lie at 02:14. Ears do."

From esmirnov@earthlink.net Wed May 17 18:55:11 1995
Path: ashpoly!bigsur!pacrim!jpgate!kamome!earthlink!esmirnov
From: esmirnov@earthlink.net (Emi Smirnov)
Newsgroups: comp.dsp
Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995May17.185511.9183@earthlink.net>
Date: Wed, 17 May 1995 18:55:11 GMT
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In article <1995May17.103711.7353@cam.ac.uk>, hhughes@cam.ac.uk (Heather Hughes) 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.

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

-- 
Emi Smirnov
Opinions expressed are solely my own and not those of EarthLink Network.
------------------------------------------------------------

From ttanaka@ox.ac.uk Thu May 18 20:06:11 1995
Path: ashpoly!cascade!transat!eunet-de!hansebox!ox!ttanaka
From: ttanaka@ox.ac.uk (Thiago Tanaka)
Newsgroups: comp.dsp
Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995May18.200611.7340@ox.ac.uk>
Date: Thu, 18 May 1995 20:06:11 GMT
References: <1995May17.103711.7353@cam.ac.uk>
Organization: Oxford University Computing Laboratory
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In article <1995May17.103711.7353@cam.ac.uk>, hhughes@cam.ac.uk (Heather Hughes) 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.

-- 
Thiago Tanaka
Tape trading list upon request. SASE required for international mail.