Date: Wed, 22 Mar 1995 20:18:49 -0800 (PST) From: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> To: PVinci@ix.netcom.com (Paul Vinciguerra) Cc: hackers@FreeBSD.org Subject: Re: ata/ide sector translation modes c/h/s vs. LBA? Message-ID: <199503230418.UAA11500@gndrsh.aac.dev.com> In-Reply-To: <199503230344.TAA12714@ix2.ix.netcom.com> from "Paul Vinciguerra" at Mar 22, 95 07:44:36 pm
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> > I know you all must now be tired of all the ATA questions, but ... > > Why does the ATA standard make such a big stink about LBA mode?? Because it is *new*, and allows you to use drives >536870912 bytes. > As I see it, either way, you have to translate either mode into: > > Sector Number > Cylinder Low > Cylinder High > Dev/Head > > So, how does LBA mode improve performance -- isn't it just a different > set of calculations that need be done before *Each* command?? Am I > missing something? It greatly simplifies the calculation for this. Basically a drive in LBA mode has 256 sectors, 16 heads and upto 1024 cylinders. The bios can then simply use OR and SHIFT to get a logical block number. I am leaving out lots of details, I have not yet unassembled awards LBA code so I am not sure of all the details, but that is the just of it. -- Rod Grimes rgrimes@gndrsh.aac.dev.com Accurate Automation Company Custom computers for FreeBSD
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