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If user set this HDD to NORMAL mode, the maximum accessible HDD size will be
528 Megabytes even though its physical size may be greater than that!
LBA (Logical Block Addressing) mode
A new HDD accessing method to overcome the 528 Megabyte bottleneck. The
number of cylinders, heads & sectors shown in setup may not be the number
physically contained in the HDD.
During HDD accessing, the IDE controller will transform the logical address
described by sector, head & cylinder into its own physical address inside the HDD.
The maximum HDD size supported by LBA mode is 8.4 Gigabytes which is obtained
by the following formula:
no. Cylinder
x
no. Head
x
no. Sector
x
bytes per sector
LARGE mode
Extended HDD access mode supported by Award Software.
Some IDE HDDs contain more than 1024 cylinder without LBA support (in some
cases, user do not want LBA). The Award BIOS provides another alternative to
support these kinds of LARGE mode:
CYLS.
1120
560
BIOS tricks DOS (or other OS) that the number of cylinders is less than 1024 by
dividing it by 2. At the same time, the number of heads is multiply by 2. Reverse
transformation process will be made inside INT 12h in order to access the right
HDD address the right HDD address!
Maximum HDD size:
no. Cylinder
x
no. Head
x
no. Sector
x
bytes per sector
NOTE: To support LBA or LARGE mode of HDDs, there must be some softwares
involved. All these softwares are located in the Award HDD Service Routine
(1NT 13h). It may be failed to access a HDD with LBA (LARGE) mode selected
if you are running under a Operating System which replaces the whole INT 13h.
(1024)
( 255)
(
( 512)
8.4 Gigabytes
HEAD
SECTOR
16
59
32
59
(1024)
(
32)
(
( 512)
1 Gigabytes
63)
MODE
NORMAL
LARGE
63)
37
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