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A major non-wintel OS handles this problem by a "partition map" in
the first few LBA's of the drive which describes the location and size
of the other partitions. The boot FW knows how to read the partition map
in either LBA mode or in CHS mode. Afterwards, the boot FW switches to a
"driver" which knows how to access the other partitions. They
are still able to boot from any partition on the drive. There is
no 8GB restriction on that OS and (of course) no user selection is
required.
...Harlan
---------------- Begin Message 1----------------
Date: 7/11/01 9:44 AM
Received: 7/11/01 10:00 AM
From: Hale Landis, [EMAIL PROTECTED]
Reply-To: Tom Colligan, [EMAIL PROTECTED]
To: [EMAIL PROTECTED], [EMAIL PROTECTED]
** This is the quasi-official and semi-temporary T13 email list server.
**
>Curtis Stevens <[EMAIL PROTECTED]> said:
>I do not understand the BIOS "Large" or "LBA CHS Translation".
>Cab you be more specific? The BIOSes I worked with in a former
>life did not have an option to enable the 4x functions and they
>were not dependent on drive size. As far as I know, the process
>remains automatic...
Large and LBA have been used to describe the two different
methods of doing CHS translation for drives >528MB and <8GB. I
think Phoenix always used or defaulted to Large. Large is the
method that was orginially used on ESDI drives when those drives
exceeded 528MB (before the time of ATA). The LBA method has been
used by SCSI adapters to emulate CHS. But in the early days of
LBA capable ATA drives, Western Digital promoted the LBA scheme.
The result was that many BIOS supported both schemes and made a
human select the one to be used by the BIOS. Large is generally
faster because it uses some simple bit shifting while LBA uses
32-bit multiple and divide.
I think the real question here is this: Do the OS folks have a
preference? I know that that an OS driver must perform a bunch
of tests (reading various CHS locations and watching the BIOS to
see what real CHS or LBA is sent to the device) to determine
which CHS translation scheme is being used.
*** Hale Landis *** [EMAIL PROTECTED] ***
*** Niwot, CO USA *** www.ata-atapi.com ***
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