From mrodriguez@delphi.com Sat Jan 07 21:39:53 1995 Path: ashpoly!cascade!transat!sunet!nordrelay!delphi!mrodriguez From: mrodriguez@delphi.com (Min-jun Rodríguez) Newsgroups: comp.dsp Subject: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jan07.213953.1628@delphi.com> Date: Sat, 07 Jan 1995 21:39:53 GMT Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: Netscape 1.1N Lines: 11 Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks. By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample. Source code in 56k assembly uploaded to ftp.ashford-poly.edu:/pub/telecom-archives/dsp56k/stardust_56k.asm. -- Min-jun Rodríguez *PLONK* filter active for trolls. Acorn RiscPC 600 - NetBSD 1.0 From ssilva@delphi.com Sun Jan 08 08:04:53 1995 Path: ashpoly!cascade!transat!sunet!nordrelay!delphi!ssilva From: ssilva@delphi.com (Sven Silva) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jan08.080453.6017@delphi.com> Date: Sun, 08 Jan 1995 08:04:53 GMT References: <1995Jan07.213953.1628@delphi.com> Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: Netscape 1.1N Lines: 9 In article <1995Jan07.213953.1628@delphi.com>, mrodriguez@delphi.com (Min-jun Rodríguez) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. > This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks. Beautiful assembly code! The 24-bit word size of the 56001 is tailor-made for high-precision audio filtering. -- Sven Silva Tape trading list upon request. SASE required for international mail. From rlindqvist@cam.ac.uk Tue Jan 10 05:59:53 1995 Path: ashpoly!cascade!bigsur!cam!rlindqvist From: rlindqvist@cam.ac.uk (Renata Lindqvist) Newsgroups: comp.dsp Subject: Re: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jan10.055953.8941@cam.ac.uk> Date: Tue, 10 Jan 1995 05:59:53 GMT References: <1995Jan07.213953.1628@delphi.com> Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: NewsWatcher 2.0b24 Lines: 11 In article <1995Jan07.213953.1628@delphi.com>, mrodriguez@delphi.com (Min-jun Rodríguez) 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. PGP Public key available via finger or upon request. -- Renata Lindqvist "Hardware is temporary. The signal survives." Macintosh IIfx / Linux 1.2.13