From mtakahashi@utexas.edu Sat Feb 18 09:10:00 1995
Path: ashpoly!cascade!transat!eunet-de!hansebox!utexas!mtakahashi
From: mtakahashi@utexas.edu (Mikhail Takahashi)
Newsgroups: comp.dsp
Subject: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Feb18.091000.5584@utexas.edu>
Date: Sat, 18 Feb 1995 09:10:00 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.

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

-- 
Mikhail Takahashi | mtakahashi@utexas.edu
PGP Key fingerprint: 155D ACA8 6F8B FD4F
"Keep the channels open."

From teriksson@netcom.com Sat Feb 18 23:28:00 1995
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From: teriksson@netcom.com (Takeshi Eriksson)
Newsgroups: comp.dsp
Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1995Feb18.232800.5089@netcom.com>
Date: Sat, 18 Feb 1995 23:28:00 GMT
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In article <1995Feb18.091000.5584@utexas.edu>, mtakahashi@utexas.edu (Mikhail Takahashi) 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.

-- 
Takeshi Eriksson
Tape trading list upon request. SASE required for international mail.