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Article #21487Re: DMA on RISC-based systems
From: Chris Maltby
Date: Mon, 29 May 1989 01:18
Date: Mon, 29 May 1989 01:18
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In article <1989May26.170247.1165@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: > Having the CPU do the copying is not an obviously *un*reasonable idea. > Much depends on the details. > DMA historically was more popular than auxiliary memory because memory was > expensive. This is no longer true. Of course, there are many benefits that can be gained by having controllers with their own buffers. Disk drivers can stop worrying about rotational placement if the disk controller is providing whole tracks or cylinders at a time for no extra bus overhead. LAN drivers can avoid copying stuff like protocol headers etc into and out of main memory. Generally, the CPU can be a lot smarter about I/O than any brain-damaged microprocessor controlled device interface. -- Chris Maltby - Softway Pty Ltd (chris@softway.sw.oz) PHONE: +61-2-698-2322 UUCP: uunet!softway.sw.oz.au!chris FAX: +61-2-699-9174 INTERNET: chris@softway.sw.oz.au
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Path: arc1-ca.pugleaf.net!utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!munnari!otc!softway!chris From: chris@softway.oz (Chris Maltby) Newsgroups: comp.arch Subject: Re: DMA on RISC-based systems Message-ID: <1552@softway.oz> Date: 29 May 89 01:18:35 GMT References: <46500067@uxe.cso.uiuc.edu> <1989May26.170247.1165@utzoo.uucp> Organization: Softway Pty Ltd, Sydney, Australia Lines: 20