From cnakamura@cmu.edu Tue Jun 07 13:58:20 1994
Path: ashpoly!cascade!transat!eunet-fr!teletel!cmu!cnakamura
From: cnakamura@cmu.edu (Callum Nakamura)
Newsgroups: comp.dsp
Subject: [FLAME] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994Jun07.135820.2629@cmu.edu>
Date: Tue, 07 Jun 1994 13:58:20 GMT
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Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.

By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample.
The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead.

Source code in 56k assembly uploaded to ftp.ashford-poly.edu:/pub/telecom-archives/dsp56k/stardust_56k.asm.

-- 
Callum Nakamura | cnakamura@cmu.edu
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"Keep the channels open."

From hlopez@mit.edu Wed Jun 08 13:04:20 1994
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From: hlopez@mit.edu (Heather López)
Newsgroups: comp.dsp
Subject: Re: [FLAME] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994Jun08.130420.1636@mit.edu>
Date: Wed, 08 Jun 1994 13:04:20 GMT
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In article <1994Jun07.135820.2629@cmu.edu>, cnakamura@cmu.edu (Callum Nakamura) writes:
> Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.
> By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample.

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

-- 
Heather López -- Massachusetts Institute of Technology
"There are 14 nodes and only 10 countries. Count again."

From ihughes@clari.net Fri Jun 10 02:15:20 1994
Path: ashpoly!cascade!transat!eunet-de!hansebox!clari!ihughes
From: ihughes@clari.net (Ines Hughes)
Newsgroups: comp.dsp
Subject: Re: [FLAME] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994Jun10.021520.9037@clari.net>
Date: Fri, 10 Jun 1994 02:15:20 GMT
References: <1994Jun07.135820.2629@cmu.edu> <1994Jun08.130420.1636@mit.edu>
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In article <1994Jun08.130420.1636@mit.edu>, hlopez@mit.edu (Heather López) writes:
> Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering.

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

-- 
Ines Hughes
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