From arobertson@stanford.edu Thu Jun 15 21:11:59 1995 Path: ashpoly!bigsur!pacrim!jpgate!kamome!stanford!arobertson From: arobertson@stanford.edu (Anton Robertson) Newsgroups: comp.dsp Subject: [SPECULATION] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jun15.211159.1057@stanford.edu> Date: Thu, 15 Jun 1995 21:11:59 GMT Organization: Stanford University Computer Systems Lab NNTP-Posting-Host: stanford.edu X-Newsreader: WinVN 0.99.5 Lines: 11 Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. This leaves over 95% of the DSP56001's 16.5 MIPS available for other audio tasks. Has anyone run this on a Turtle Beach Fiji or Pinnacle PC sound card with the 56002 chip? -- Anton Robertson Hayes Optima 288 @ 9600 Telebit bps "Measuring a record you own is listening, not piracy." From nsuzuki@cam.ac.uk Fri Jun 16 09:44:59 1995 Path: ashpoly!cascade!transat!ukc!fennimore!cam!nsuzuki From: nsuzuki@cam.ac.uk (Nadine Suzuki) Newsgroups: comp.dsp Subject: Re: [SPECULATION] Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jun16.094459.5759@cam.ac.uk> Date: Fri, 16 Jun 1995 09:44:59 GMT References: <1995Jun15.211159.1057@stanford.edu> Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1995Jun15.211159.1057@stanford.edu>, arobertson@stanford.edu (Anton Robertson) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. > However, when downsampling from 44.1 kHz to 64 Hz, accumulator overflow in the biquad IIR filter can destabilize the loop. Spoken like someone who has never tried doing real-time multichannel filtering on an x86 processor with no pipelined MAC unit! -- Nadine Suzuki | nsuzuki@cam.ac.uk PGP Key fingerprint: DF11 CFAA 67F7 56C1 "Keep the channels open."