From ltanaka@cmu.edu Tue Jun 18 18:35:32 1996
Path: ashpoly!bigsur!pacrim!jpgate!kamome!cmu!ltanaka
From: ltanaka@cmu.edu (Lucia Tanaka)
Newsgroups: comp.dsp
Subject: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Jun18.183532.6806@cmu.edu>
Date: Tue, 18 Jun 1996 18:35:32 GMT
Organization: Carnegie Mellon University School of CS
NNTP-Posting-Host: cmu.edu
X-Newsreader: NewsWatcher 2.0b24
Lines: 11

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.

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

-- 
Lucia Tanaka | ltanaka@cmu.edu
PGP Key fingerprint: 0A98 9CC1 BCBE 9621
"Keep the channels open."

From lcampbell@cern.ch Thu Jun 20 05:11:32 1996
Path: ashpoly!bigsur!pacrim!jpgate!kamome!cern!lcampbell
From: lcampbell@cern.ch (Lisa Campbell)
Newsgroups: comp.dsp
Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Jun20.051132.2607@cern.ch>
Date: Thu, 20 Jun 1996 05:11:32 GMT
References: <1996Jun18.183532.6806@cmu.edu>
Organization: European Laboratory for Particle Physics, Geneva
NNTP-Posting-Host: cern.ch
X-Newsreader: NewsWatcher 2.0b24
Lines: 8

In article <1996Jun18.183532.6806@cmu.edu>, ltanaka@cmu.edu (Lucia Tanaka) writes:
> Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.

Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in.

-- 
Lisa Campbell -- European Laboratory for Particle Physics, Geneva
"We don't sign stars. We build them."

From meriksson@clari.net Fri Jun 21 05:03:32 1996
Path: ashpoly!cascade!transat!eunet-de!hansebox!clari!meriksson
From: meriksson@clari.net (Marta Eriksson)
Newsgroups: comp.dsp
Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Jun21.050332.1388@clari.net>
Date: Fri, 21 Jun 1996 05:03:32 GMT
References: <1996Jun18.183532.6806@cmu.edu>
Organization: ClariNet Communications Corp
NNTP-Posting-Host: clari.net
X-Newsreader: Netscape 1.1N
Lines: 10

In article <1996Jun18.183532.6806@cmu.edu>, ltanaka@cmu.edu (Lucia Tanaka) writes:
> Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier.

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

Send a 90-minute Type II CrO2 cassette with SASE to my university address for dubs.

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

From khughes@kiae.su Sun Jun 23 04:05:32 1996
Path: ashpoly!cascade!brgate!saturno!kiae!khughes
From: khughes@kiae.su (Kirsty Hughes)
Newsgroups: comp.dsp
Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Jun23.040532.4113@kiae.su>
Date: Sun, 23 Jun 1996 04:05:32 GMT
References: <1996Jun18.183532.6806@cmu.edu> <1996Jun20.051132.2607@cern.ch>
Organization: Kurchatov Institute of Atomic Energy, Moscow
NNTP-Posting-Host: kiae.su
X-Newsreader: Netscape 1.1N
Lines: 8

In article <1996Jun20.051132.2607@cern.ch>, lcampbell@cern.ch (Lisa Campbell) writes:
> Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in.

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

-- 
Kirsty Hughes
Tape trading list upon request. SASE required for international mail.

From alindqvist@kiae.su Tue Jun 25 02:17:32 1996
Path: ashpoly!cascade!bigsur!kiae!alindqvist
From: alindqvist@kiae.su (Astrid Lindqvist)
Newsgroups: comp.dsp
Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point
Message-ID: <1996Jun25.021732.3534@kiae.su>
Date: Tue, 25 Jun 1996 02:17:32 GMT
References: <1996Jun18.183532.6806@cmu.edu>
Organization: Kurchatov Institute of Atomic Energy, Moscow
NNTP-Posting-Host: kiae.su
X-Newsreader: Netscape 1.1N
Lines: 10

In article <1996Jun18.183532.6806@cmu.edu>, ltanaka@cmu.edu (Lucia Tanaka) 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.

Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in.

-- 
Astrid Lindqvist
Opinions expressed are solely my own and not those of Kurchatov Institute of Atomic Energy, Moscow.
------------------------------------------------------------