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> > > your terminology > > ... I'm more confident in algebra than in English ... > > If [D = H] is the way it "has to be" ... what makes it so? > "Mcgrath, Jim" <[EMAIL PROTECTED]> 01/02/02 02:09PM > ... Put another way, have you ever seen a SCSI logic analyzer trace > where H <> D on a successful command? Anything short of that > does not tell us ... Ouch, ouch, ouch. Nuts. I still think we must not be meaning the same things by the same words? H is not precisely visible in an 8 bit asynchronous Scsi trace. It is explicitly visible in Usb/1394 trace. H <> 0 is close to visible in an Ide Dma trace: few hosts there DMACK- when H = 0. When I say I have Scsi traces of H != D, by definition I'm saying that I peeked at H somewhere out of band. For example, suppose I allocate an aligned 4KiB physical page and ask the i/o layer to move H = 4KiB and then settle for the x24 bytes that some Scsi device I have moves in response to the cb x 12 0 0 0 FF 0. Then I only know Di < Hi because I know Hi because I traced it inside the host. The asynchronous Scsi trace doesn't show me that my Hi = 4KiB. The port to Atapi from Scsi breaks in the way I mean to be discussing precisely because Atapi makes H more visible. "Change Is Bad" in plug 'n play: anything new I make visible I can find somebody on the other end of the cable to trip over. I see the workaround in Atapi Pio for making H typically not matter even though visible, I see no corresponding workaround in Atapi Dma. I see the standard does not mention the workaround that works in Atapi Pio. I think the standard has to change (or people have to extend it bilaterally) if we want a workaround to work in Atapi Dma. Pat LaVarre Subscribe/Unsubscribe instructions can be found at www.t13.org.
