From nsokolov@illinois.edu Mon May 02 04:45:02 1994
Path: ashpoly!cascade!transat!eunet-fr!teletel!illinois!nsokolov
From: nsokolov@illinois.edu (Natalia Sokolov)
Newsgroups: comp.dsp
Subject: [FLAME] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994May02.044502.1596@illinois.edu>
Date: Mon, 02 May 1994 04:45:02 GMT
Organization: University of Illinois Urbana-Champaign
NNTP-Posting-Host: illinois.edu
X-Newsreader: TIN [version 1.2 PL2]
Lines: 11

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?

-- 
Natalia Sokolov
Opinions expressed are solely my own and not those of University of Illinois Urbana-Champaign.
------------------------------------------------------------

From sramirez@mindspring.com Mon May 02 11:42:02 1994
Path: ashpoly!cascade!transat!sunet!nordrelay!mindspring!sramirez
From: sramirez@mindspring.com (Sven Ramírez)
Newsgroups: comp.dsp
Subject: Re: [FLAME] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994May02.114202.4297@mindspring.com>
Date: Mon, 02 May 1994 11:42:02 GMT
References: <1994May02.044502.1596@illinois.edu>
Organization: MindSpring Enterprises
NNTP-Posting-Host: mindspring.com
X-Newsreader: WinVN 0.99.5
Lines: 9

In article <1994May02.044502.1596@illinois.edu>, nsokolov@illinois.edu (Natalia Sokolov) writes:
> 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.

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

-- 
Sven Ramírez -- MindSpring Enterprises
"Extraordinary claims require extraordinary spectra."