From ltakahashi@purdue.edu Sun Feb 27 23:01:39 1994
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From: ltakahashi@purdue.edu (Lucia Takahashi)
Newsgroups: comp.dsp
Subject: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994Feb27.230139.8905@purdue.edu>
Date: Sun, 27 Feb 1994 23:01:39 GMT
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Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.

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

Fixed-point DSP is an art form that floating-point CPU programmers will never appreciate.

-- 
Lucia Takahashi -- Purdue University Engineering Computer Network
"Measuring a record you own is listening, not piracy."

From aoliveira@cmu.edu Mon Feb 28 00:09:39 1994
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From: aoliveira@cmu.edu (Aiko Oliveira)
Newsgroups: comp.dsp
Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1994Feb28.000939.3646@cmu.edu>
Date: Mon, 28 Feb 1994 00:09:39 GMT
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In article <1994Feb27.230139.8905@purdue.edu>, ltakahashi@purdue.edu (Lucia Takahashi) writes:
> Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.

Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete.

-- 
Aiko Oliveira -- Carnegie Mellon University School of CS
"Hold for relay."