Do we still need ATA disk CHS addressing?

Erik Trulsson ertr1013 at
Mon Aug 10 19:19:11 UTC 2009

On Mon, Aug 10, 2009 at 08:38:16PM +0200, Dag-Erling Smørgrav wrote:
> "Julian H. Stacey" <jhs at> writes:
> > Alexander Motin <mav at> writes:
> > > Have anybody seen ATA drive without LBA support in last years?
> > Yes
> Have you really, or did you just assume that "old" means "no LBA"?
> > I run 20+ assorted hosts from 4.11 to 7.2 Uni & Dual proc, i386 (real 386!)
> > to 686 & amd64 so I guess I'm 
> >   A) Pretty vulnerable to legacy scare.
> >   B) A litmus tesst for a wider community of others, some  with older kit, 
> >      not on lists or with bleeding edge latest hardware, but will 
> >      get hit when stuff eg HCS gets declared legacy=dumped.
> Do you seriously intend to run FreeBSD 9 on kit that is too old to
> support LBA?  We're talking early nineties here.  CHS doesn't scale past
> 504 MB, so any ATA disk larger than that must peforce support LBA.  I
> bought my first 1 GB drive (Connor CFP1080) in 1995.

Actually I believe even the very first version of the ATA standard (long
before support for LBA or any other modern features was added) could handle
larger disks than 504MiB.  I think the original limit of ATA was 2.1 GB. 
The 504MiB limit was actually the intersection between the limits of the PC
BIOS and the limits of the ATA standard.  (ATA and the BIOS had different
number of bits used to indicate each of cylinder, head and sector.  When you
took the lower number of bits for each you ended up with the 504MiB limit.)

<Insert your favourite quote here.>
Erik Trulsson
ertr1013 at

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