Date: Thu, 23 Mar 1995 16:47:34 +1000 From: Bruce Evans <bde@zeta.org.au> To: PVinci@ix.netcom.com, rgrimes@gndrsh.aac.dev.com Cc: hackers@FreeBSD.org Subject: Re: ata/ide sector translation modes c/h/s vs. LBA? Message-ID: <199503230647.QAA04580@godzilla.zeta.org.au>
next in thread | raw e-mail | index | archive | help
>> 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.
No. Even the old ATA standard specifies addressing drives with
65535(+1?) * 16 * 255 sectors (almost 128GB). LBA only increases
the limit to 65536 * 16 * 256. See
"Yet Another ATA-2/Fast-ATA/EIDE FAQ" in
comp.sys.ibm.pc.hardware.storage.
>It greatly simplifies the calculation for this. Basically a drive
^slightly
>in LBA mode has 256 sectors, 16 heads and upto 1024 cylinders.
Up to 65536 or 65536 cylinders. Oops, in previous mail I said that LBA
addresses are 24 bits. They are actually 28 bits (4 more in the old
head bits). The bits are rearranged (the head bits become bits 24-27
of the LBA, and the braindamaged 1-based sector numbers are gone), so
it is only a heuristic to think of the translation as giving a 256S * 16H
geometry.
Bruce
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199503230647.QAA04580>