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If you set your HDD to Normal mode, the maximum accessible HDD will
be 528 megabytes even though the physical size of the HDD may be
greater than that.
LBA (Logical Block Addressing) Mode
LBA mode is a HDD accessing method to overcome the 528 megabyte
limitation. The number of cylinders, heads and sectors shown on the
screen may not be the actual number for the HDD.
During HDD accessing, the IDE controller will transform the logical ad-
dress described by the sector, head and cylinder number into its own
physical address inside the HDD.
The maximum HDD size supported by the LBA mode is 8.4 gigabytes. It
is obtained by the following formula.
no. Cylinders (1024)
x no. Heads ( 255)
x no. Sectors ( 63)
x bytes per sector ( 512)
8.4 gigabytes
Large Mode
Large mode is the extended HDD access mode supported by the sys-
tem board. Some IDE HDDs have more than 1024 cylinders without
LBA support (in some cases, you may not want the LBA mode). This
system board provides another alternative to support these kinds of
HDDs.
The BIOS tells the operating system that the number of cylinders is half
the actual number and that the number of heads is double the actual
number. During disk access, the reverse conversion is done by the
INT13h routine.