Path: csiph.com!weretis.net!feeder6.news.weretis.net!feeder.usenetexpress.com!feeder-in1.iad1.usenetexpress.com!border1.nntp.dca1.giganews.com!border2.nntp.dca1.giganews.com!nntp.giganews.com!news.iecc.com!.POSTED.news.iecc.com!nerds-end From: David Brown Newsgroups: comp.compilers Subject: Re: C compiler pointer management on DSPs Date: Sun, 29 Sep 2019 10:53:35 +0200 Organization: A noiseless patient Spider Lines: 25 Sender: news@iecc.com Approved: comp.compilers@iecc.com Message-ID: <19-09-018@comp.compilers> References: <19-09-003@comp.compilers> <19-09-004@comp.compilers> <19-09-006@comp.compilers> <19-09-007@comp.compilers> <19-09-009@comp.compilers> <19-09-015@comp.compilers> <19-09-017@comp.compilers> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Info: gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="96365"; mail-complaints-to="abuse@iecc.com" Keywords: DSP, architecture, C Posted-Date: 30 Sep 2019 18:06:34 EDT X-submission-address: compilers@iecc.com X-moderator-address: compilers-request@iecc.com X-FAQ-and-archives: http://compilers.iecc.com Content-Language: en-GB Xref: csiph.com comp.compilers:2368 On 28/09/2019 20:19, Derek M. Jones wrote: > George, > >> Just curious - what DSPs have 48-bit characters? > > Motorola DSP56000 Family Optimizing C Compiler uses 24 bits > TMS320C3x/C4x Optimizing C Compiler uses 32 bits > > I remember reading a compiler manual and thinking, wow, that's > unusual. 24-bit DSP's have been popular for audio applications. (There is also the TPU, a specialised RISC processor used for timer applications in engine control microcontrollers, that is 24-bit.) Some processors have larger access sizes to simplify the hardware. The first DEC Alpha, and some ARM designs, had no instructions for reading or writing 8-bit or 16-bit data. In effect, these had 32-bit (maybe on the Alpha it was 64-bit) "byte" sizes. But smaller access sizes could be easily simulated in software. I can't think of any application where 48-bit would such a natural fit that you'd have it as your basic access unit. Some video DSP's have used 48-bit units, but that is for a vector of 3 16-bit colour units.