From sivanov@netcom.com Sun Feb 12 11:19:47 1995 Path: ashpoly!cascade!transat!sunet!nordrelay!netcom!sivanov From: sivanov@netcom.com (Steve Ivanov) Newsgroups: comp.dsp Subject: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Feb12.111947.7368@netcom.com> Date: Sun, 12 Feb 1995 11:19:47 GMT Organization: NETCOM On-Line Communication Services NNTP-Posting-Host: netcom.com X-Newsreader: NewsWatcher 2.0b24 Lines: 11 Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. 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. -- Steve Ivanov Opinions expressed are solely my own and not those of NETCOM On-Line Communication Services. ------------------------------------------------------------ From gokonkwo@cam.ac.uk Mon Feb 13 11:53:47 1995 Path: ashpoly!cascade!brgate!saturno!cam!gokonkwo From: gokonkwo@cam.ac.uk (Graham Okonkwo) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Feb13.115347.3562@cam.ac.uk> Date: Mon, 13 Feb 1995 11:53:47 GMT References: <1995Feb12.111947.7368@netcom.com> Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: TIN [version 1.2 PL2] Lines: 9 In article <1995Feb12.111947.7368@netcom.com>, sivanov@netcom.com (Steve Ivanov) writes: > Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. -- Graham Okonkwo *PLONK* filter active for trolls. Atari Falcon 030 - NetBSD 1.0 From bdubois@ox.ac.uk Tue Feb 14 06:20:47 1995 Path: ashpoly!cascade!transat!sunet!nordrelay!ox!bdubois From: bdubois@ox.ac.uk (Bill Dubois) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Feb14.062047.1690@ox.ac.uk> Date: Tue, 14 Feb 1995 06:20:47 GMT References: <1995Feb12.111947.7368@netcom.com> Organization: Oxford University Computing Laboratory NNTP-Posting-Host: ox.ac.uk X-Newsreader: NewsWatcher 2.0b24 Lines: 9 In article <1995Feb12.111947.7368@netcom.com>, sivanov@netcom.com (Steve Ivanov) writes: > Optimizing the Stardust Costas loop demodulator for the Motorola DSP56001 chip. Real programmers write in C, not arcane DSP microcode. With Pentium chips hitting 100 MHz, dedicated DSPs are obsolete. -- Bill Dubois "They will send a copy in my place." Acorn RiscPC 600 / System 7.5.1