| Auto-Detecting Large
ATA (IDE) Disc Drives Why
The original IBM PC BIOS had a capacity
limitation of 528MB. The original interrupt for block devices (floppy drives and hard disc
drives), called INT13,
had a maximum definition of 1024 Cylinders, 256 Heads, and 63 Sectors per track. Using 512
bytes per sector, a grand total of 8.4 Gbytes is possible using CHS translation.
Concurrently, ATA (IDE) disc drives have utilized CHS default translation parameters that
also have a maximum of 8.4 Gbytes (16,383 Cylinders, 16 Heads, and 63 Sectors per track).
ATA drives greater than 8.4 Gbytes rely on total sectors to determine the actual capacity
of the drive, not CHS.
Later BIOS's would use LBA assisted
translation to access capacities beyond 528 Mbytes up to 8.4 Gbytes. Today disc drives
with capacity points beyond 8.4 Gbytes do not use CHS translation in BIOS. Instead, they
use LBA auto-detection to address the drive's full capacity.
What To Do
Select
automatic drive detection if available. Choosing this option automatically configures the
computer for your new drive.
If your
BIOS does not provide automatic drive detection, select "user-defined" drive
settings and enter the CHS values. CHS values support drive capacities up to 8.4 Gbytes.
Verify that
LBA mode is enabled. Many BIOS use the logical block addressing (LBA) mode to access
drives with capacities greater than 528 Mbytes. Most BIOSs automatically set this mode
during the auto-detection process.
We recommend you use DiscWizard to evaluate
your BIOS and determine whether your system needs additional
BIOS support. For more information, see the DiscWizard
Homepage.
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