Date: Wed, 14 Oct 1998 12:43:23 +1000 From: John Saunders <john.saunders@scitec.com.au> To: "freebsd-current@FreeBSD.ORG" <freebsd-current@FreeBSD.ORG> Subject: RE: bitten 3 times already. Message-ID: <01BDF770.3BFBAFB0.john.saunders@scitec.com.au>
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Soren Schmidt [SMTP:sos@FreeBSD.ORG] wrote:
> In reply to Marius Bendiksen who wrote:
> > I haven't been tracking this too closely, but doesn't such a thing as Soren
> > Schmidt suggested (removing LBA support) mean that people with LBA drives
> > will end up in heaps of trouble? I have 8.4 + 3.2 gigs on LBA-formatted IDE
> > drives, and would certainly not appreciate losing those.
>
> You dont need to run the drive in LBA mode to coexist with DOS or whatever.
> Also you dont need to run the drive in LBA mode to use >8G, infact using
> LBA has nothing to do with >8G support. >8G support has something to do
> with us probing the drive correctly and using it that way.
I think people are confusing operating the physical interface
to the drive (IDE interface) in LBA mode, and using the partition
geometry calculated by the BIOS in LBA mode.
>From what I can understand, FreeBSD uses the sector addresses
rather than the CHS addresses in the partition table to
determine where it's partition lives. It is then free to either
put the drive into LBA mode or CHS mode as long as it ends up
reading and writing to the correct sectors. If it leaves the
drive in CHS mode, then it has to make absolutely sure it knows
the correct geometry for the drive so it can convert the sector
addresses into the exact CHS values for the drive when doing IO.
P.S. The above view is based on observation of installing FreeBSD
on many machines, and "manager level" IDE/ATAPI knowledge, rather
than intimate knowledge of the IDE driver source code. So feel
free to correct me if needed :-)
Cheers.
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