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Xref: sserve comp.os.386bsd.development:1713 comp.unix.bsd:13318 Newsgroups: comp.os.386bsd.development,comp.unix.bsd Path: sserve!newshost.anu.edu.au!munnari.oz.au!bunyip.cc.uq.oz.au!harbinger.cc.monash.edu.au!yeshua.marcam.com!usc!howland.reston.ans.net!cs.utexas.edu!uunet!elroy.jpl.nasa.gov!decwrl!netcomsv!netcom.com!jmonroy From: jmonroy@netcom.com (Jesus Monroy Jr) Subject: Re: Late comments on the DMA problem. Message-ID: <jmonroyCK2t6n.1pM@netcom.com> Organization: NETCOM On-line Communication Services (408 241-9760 guest) X-Newsreader: TIN [version 1.2 PL1] References: <jmonroyCJy610.HB7@netcom.com> <1994Jan21.095505.8375@cc.usu.edu> Date: Sun, 23 Jan 1994 09:32:46 GMT Lines: 44 ivie@cc.usu.edu wrote: : In article <jmonroyCJy610.HB7@netcom.com>, jmonroy@netcom.com (Jesus Monroy Jr) writes: : >>> For example, it is not possible to implment "scatter/gather" with the FDC by : >>> ^^^ : > ||| : > I think he meant to say that "it is possible", because I know : > it is. Evidence is the the FDC (flexible drive controller) : > has a command for read-a-track. : Yes, but "scatter/gather" has nothing to do with the FDC's read-a-track : :: [deleted stuff] :: : Yes, I know what scatter/gather is (I hope otther people do). However, I interpeed his statements as saying: You can't issue a new DMA command in the middle of a large buffer transaction (read-a-track.) The latency time is just too much. This is what I had not considered. I (do) know that the buffer gets sorted (via (xx)sort routine). So it is possible that the software may be doing a sort-of "scatter-gather"... Yes, I know that "s-g" is a hardware thing, but the real point is... is there a DMA transaction that may propogate a delay. My answer is: I'll have to look in to it. Then again, there probable somethin in my in-box that says.. "your a jerk buddy". : Since you can't get an interrupt to tell you that the DMA controller has : finished doing a page, you can't reload the DMA addresses when the end of : a page is reached. : please define page. your message is ambiguous. -- Jesus Monroy Jr jmonroy@netcom.com Zebra Research /386BSD/device-drivers /fd /qic /clock /documentation ___________________________________________________________________________