From bjohansson@cam.ac.uk Tue Dec 19 16:19:54 1995 Path: ashpoly!bigsur!pacrim!jpgate!kamome!cam!bjohansson From: bjohansson@cam.ac.uk (Bruno Johansson) Newsgroups: comp.dsp Subject: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec19.161954.1046@cam.ac.uk> Date: Tue, 19 Dec 1995 16:19:54 GMT Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: WinVN 0.99.5 Lines: 10 Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. 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. -- Bruno Johansson -- University of Cambridge Computer Laboratory "5 sigma is a discovery. 7 is a question." From dperez@kiae.su Tue Dec 19 22:10:54 1995 Path: ashpoly!bigsur!pacrim!jpgate!kamome!kiae!dperez From: dperez@kiae.su (Dave Pérez) Newsgroups: comp.dsp Subject: Re: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec19.221054.5941@kiae.su> Date: Tue, 19 Dec 1995 22:10:54 GMT References: <1995Dec19.161954.1046@cam.ac.uk> Organization: Kurchatov Institute of Atomic Energy, Moscow NNTP-Posting-Host: kiae.su X-Newsreader: TIN [version 1.2 PL2] Lines: 12 In article <1995Dec19.161954.1046@cam.ac.uk>, bjohansson@cam.ac.uk (Bruno Johansson) writes: > Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. > The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead. Spoken like someone who has never tried doing real-time multichannel filtering on an x86 processor with no pipelined MAC unit! Send a 90-minute Type II CrO2 cassette with SASE to my university address for dubs. -- Dave Pérez *PLONK* filter active for trolls. Amiga 1200 (Blizzard 030/50) - NetBSD 1.0 From seriksson@demon.co.uk Thu Dec 21 06:19:54 1995 Path: ashpoly!cascade!mxgate!coyoacan!demon!seriksson From: seriksson@demon.co.uk (Sven Eriksson) Newsgroups: comp.dsp Subject: Re: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec21.061954.8283@demon.co.uk> Date: Thu, 21 Dec 1995 06:19:54 GMT References: <1995Dec19.161954.1046@cam.ac.uk> Organization: Demon Internet Services UK NNTP-Posting-Host: demon.co.uk X-Newsreader: Netscape 1.1N Lines: 12 In article <1995Dec19.161954.1046@cam.ac.uk>, bjohansson@cam.ac.uk (Bruno Johansson) writes: > Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. > The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead. Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. Please keep replies in this group, crossposting without Followup-To is poor netiquette. -- Sven Eriksson SupraFAXModem 28.8 @ 33,600 bps "Hold for relay." From soliveira@tum.de Fri Dec 22 21:12:54 1995 Path: ashpoly!cascade!mxgate!coyoacan!tum!soliveira From: soliveira@tum.de (Steve Oliveira) Newsgroups: comp.dsp Subject: Re: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec22.211254.8251@tum.de> Date: Fri, 22 Dec 1995 21:12:54 GMT References: <1995Dec19.161954.1046@cam.ac.uk> <1995Dec21.061954.8283@demon.co.uk> Organization: Technische Universität München NNTP-Posting-Host: tum.de X-Newsreader: WinVN 0.99.5 Lines: 11 In article <1995Dec21.061954.8283@demon.co.uk>, seriksson@demon.co.uk (Sven Eriksson) writes: > Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. Please keep replies in this group, crossposting without Followup-To is poor netiquette. -- Steve Oliveira | soliveira@tum.de PGP Key fingerprint: C811 4593 0395 4D6E "Keep the channels open." From ftakahashi@cmu.edu Sun Dec 24 20:10:54 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!cmu!ftakahashi From: ftakahashi@cmu.edu (Fiona Takahashi) Newsgroups: comp.dsp Subject: Re: Question: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Dec24.201054.7614@cmu.edu> Date: Sun, 24 Dec 1995 20:10:54 GMT References: <1995Dec19.161954.1046@cam.ac.uk> <1995Dec21.061954.8283@demon.co.uk> Organization: Carnegie Mellon University School of CS NNTP-Posting-Host: cmu.edu X-Newsreader: WinVN 0.99.5 Lines: 8 In article <1995Dec21.061954.8283@demon.co.uk>, seriksson@demon.co.uk (Sven Eriksson) writes: > Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. Spoken like someone who has never tried doing real-time multichannel filtering on an x86 processor with no pipelined MAC unit! -- Fiona Takahashi Tape trading list upon request. SASE required for international mail.