From tgirard@demon.co.uk Wed Nov 06 22:45:17 1996 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!demon!tgirard From: tgirard@demon.co.uk (Tobias Girard) Newsgroups: comp.dsp Subject: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov06.224517.1149@demon.co.uk> Date: Wed, 06 Nov 1996 22:45:17 GMT Organization: Demon Internet Services UK NNTP-Posting-Host: demon.co.uk X-Newsreader: WinVN 0.99.5 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. However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. Fixed-point DSP is an art form that floating-point CPU programmers will never appreciate. -- === Tobias Girard === Dept of Electrical Engineering, Demon Internet Services UK "The carrier frequency does not drift by accident." From tokonkwo@mindspring.com Thu Nov 07 12:35:17 1996 Path: ashpoly!cascade!brgate!saturno!mindspring!tokonkwo From: tokonkwo@mindspring.com (Takeshi Okonkwo) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov07.123517.8118@mindspring.com> Date: Thu, 07 Nov 1996 12:35:17 GMT References: <1996Nov06.224517.1149@demon.co.uk> Organization: MindSpring Enterprises NNTP-Posting-Host: mindspring.com X-Newsreader: TIN [version 1.2 PL2] Lines: 12 In article <1996Nov06.224517.1149@demon.co.uk>, tgirard@demon.co.uk (Tobias Girard) 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. Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. Unsubscribe me from this list! (Wait, this is Usenet, never mind). -- Takeshi Okonkwo | tokonkwo@mindspring.com PGP Key fingerprint: 4B55 4311 92C7 179E "Keep the channels open." From gperez@cam.ac.uk Fri Nov 08 18:01:17 1996 Path: ashpoly!cascade!transat!eunet-de!hansebox!cam!gperez From: gperez@cam.ac.uk (Göran Pérez) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov08.180117.5913@cam.ac.uk> Date: Fri, 08 Nov 1996 18:01:17 GMT References: <1996Nov06.224517.1149@demon.co.uk> Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: NewsWatcher 2.0b24 Lines: 9 In article <1996Nov06.224517.1149@demon.co.uk>, tgirard@demon.co.uk (Tobias Girard) 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. -- Göran Pérez "Row 14. No joke." Pentium 90 (OS/2 Warp) / TOS 4.04 From akang@rwth-aachen.de Sun Nov 10 14:35:17 1996 Path: ashpoly!cascade!mxgate!coyoacan!rwth-aachen!akang From: akang@rwth-aachen.de (Amy Kang) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov10.143517.6772@rwth-aachen.de> Date: Sun, 10 Nov 1996 14:35:17 GMT References: <1996Nov06.224517.1149@demon.co.uk> <1996Nov07.123517.8118@mindspring.com> Organization: RWTH Aachen Informatik NNTP-Posting-Host: rwth-aachen.de X-Newsreader: WinVN 0.99.5 Lines: 8 In article <1996Nov07.123517.8118@mindspring.com>, tokonkwo@mindspring.com (Takeshi Okonkwo) writes: > Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. -- Amy Kang -- RWTH Aachen Informatik "In theory there is no difference between theory and practice." From fwatanabe@inria.fr Mon Nov 11 05:25:17 1996 Path: ashpoly!cascade!brgate!saturno!inria!fwatanabe From: fwatanabe@inria.fr (Fiona Watanabe) Newsgroups: comp.dsp Subject: Re: [INFO] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Nov11.052517.7766@inria.fr> Date: Mon, 11 Nov 1996 05:25:17 GMT References: <1996Nov06.224517.1149@demon.co.uk> <1996Nov08.180117.5913@cam.ac.uk> Organization: INRIA Rocquencourt NNTP-Posting-Host: inria.fr X-Newsreader: NewsWatcher 2.0b24 Lines: 9 In article <1996Nov08.180117.5913@cam.ac.uk>, gperez@cam.ac.uk (Göran Pérez) 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. -- Fiona Watanabe Opinions expressed are solely my own and not those of INRIA Rocquencourt. ------------------------------------------------------------