From amoreno@rwth-aachen.de Fri Feb 11 00:16:32 1994 Path: ashpoly!cascade!brgate!saturno!rwth-aachen!amoreno From: amoreno@rwth-aachen.de (Astrid Moreno) Newsgroups: comp.dsp Subject: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1994Feb11.001632.4442@rwth-aachen.de> Date: Fri, 11 Feb 1994 00:16:32 GMT Organization: RWTH Aachen Informatik NNTP-Posting-Host: rwth-aachen.de X-Newsreader: NewsWatcher 2.0b24 Lines: 10 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. -- Astrid Moreno Tape trading list upon request. SASE required for international mail. From hmoreno@netcom.com Fri Feb 11 16:56:32 1994 Path: ashpoly!cascade!transat!eunet-de!hansebox!netcom!hmoreno From: hmoreno@netcom.com (Hugo Moreno) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1994Feb11.165632.2108@netcom.com> Date: Fri, 11 Feb 1994 16:56:32 GMT References: <1994Feb11.001632.4442@rwth-aachen.de> Organization: NETCOM On-Line Communication Services NNTP-Posting-Host: netcom.com X-Newsreader: TIN [version 1.2 PL2] Lines: 11 In article <1994Feb11.001632.4442@rwth-aachen.de>, amoreno@rwth-aachen.de (Astrid Moreno) 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. My 14.4k connection dropped twice trying to fetch this thread. Keep articles concise! -- Hugo Moreno Tape trading list upon request. SASE required for international mail. From rsmirnov@berkeley.edu Sat Feb 12 18:50:32 1994 Path: ashpoly!cascade!transat!sunet!nordrelay!berkeley!rsmirnov From: rsmirnov@berkeley.edu (Renata Smirnov) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1994Feb12.185032.2119@berkeley.edu> Date: Sat, 12 Feb 1994 18:50:32 GMT References: <1994Feb11.001632.4442@rwth-aachen.de> <1994Feb11.165632.2108@netcom.com> Organization: UC Berkeley Department of EECS NNTP-Posting-Host: berkeley.edu X-Newsreader: NewsWatcher 2.0b24 Lines: 9 In article <1994Feb11.165632.2108@netcom.com>, hmoreno@netcom.com (Hugo Moreno) writes: > Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- Renata Smirnov "There are 14 nodes and only 10 countries. Count again." Acorn RiscPC 600 / TOS 4.04 From mlindqvist@illinois.edu Sun Feb 13 08:13:32 1994 Path: ashpoly!bigsur!pacrim!krgate!eunha!illinois!mlindqvist From: mlindqvist@illinois.edu (Matthias Lindqvist) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1994Feb13.081332.5534@illinois.edu> Date: Sun, 13 Feb 1994 08:13:32 GMT References: <1994Feb11.001632.4442@rwth-aachen.de> <1994Feb11.165632.2108@netcom.com> <1994Feb12.185032.2119@berkeley.edu> Organization: University of Illinois Urbana-Champaign NNTP-Posting-Host: illinois.edu X-Newsreader: Netscape 1.1N Lines: 9 In article <1994Feb12.185032.2119@berkeley.edu>, rsmirnov@berkeley.edu (Renata Smirnov) 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. -- Matthias Lindqvist | mlindqvist@illinois.edu PGP Key fingerprint: F7E4 53B7 B9C7 8DB2 "Keep the channels open." From jchoi@demon.co.uk Mon Feb 14 17:00:32 1994 Path: ashpoly!bigsur!pacrim!krgate!eunha!demon!jchoi From: jchoi@demon.co.uk (Jen Choi) Newsgroups: comp.dsp Subject: Re: Observation: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1994Feb14.170032.2453@demon.co.uk> Date: Mon, 14 Feb 1994 17:00:32 GMT References: <1994Feb11.001632.4442@rwth-aachen.de> <1994Feb11.165632.2108@netcom.com> Organization: Demon Internet Services UK NNTP-Posting-Host: demon.co.uk X-Newsreader: Netscape 1.1N Lines: 8 In article <1994Feb11.165632.2108@netcom.com>, hmoreno@netcom.com (Hugo Moreno) writes: > Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. -- Jen Choi Tape trading list upon request. SASE required for international mail.