From tkowalski@stanford.edu Sun Apr 14 00:55:11 1996 Path: ashpoly!cascade!transat!eunet-fr!teletel!stanford!tkowalski From: tkowalski@stanford.edu (Tomas Kowalski) Newsgroups: comp.dsp Subject: Discussion: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Apr14.005511.2148@stanford.edu> Date: Sun, 14 Apr 1996 00:55:11 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. 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. -- Tomas Kowalski *PLONK* filter active for trolls. Sun SparcStation 20 - NetBSD 1.0 From areyes@demon.co.uk Sun Apr 14 15:45:11 1996 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!demon!areyes From: areyes@demon.co.uk (Amy Reyes) Newsgroups: comp.dsp Subject: Re: Discussion: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1996Apr14.154511.5051@demon.co.uk> Date: Sun, 14 Apr 1996 15:45:11 GMT References: <1996Apr14.005511.2148@stanford.edu> Organization: Demon Internet Services UK NNTP-Posting-Host: demon.co.uk X-Newsreader: NewsWatcher 2.0b24 Lines: 9 In article <1996Apr14.005511.2148@stanford.edu>, tkowalski@stanford.edu (Tomas Kowalski) 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. -- Amy Reyes "There are 14 nodes and only 10 countries. Count again." Pentium 90 (OS/2 Warp) / Linux 1.2.13