72 User's Manual
( III ) LARGE mode
Extended HDD access mode supported by Award Software.
Some IDE HDDs contain more than 1024 cylinder without LBA
support. The 541 Award BIOS provides another alternative to sup-
port these kinds of HDD !
Example of LARGE mode
CYLS.
HEADS SECTOR MODE
1120
16
59
NORMAL
560
32
59
LARGE
BIOS tricks DOS that the number of cylinders is less than 1024 by
dividing it by 2. At the same time, the number of heads is multi-
plied by 2. A reverse transformation process will be made inside
INT13h in order to access the right HDD address the right HDD
address!
Maximum HDD size
no. Cylinder
(1024)
x no. Head
( 32)
x no. Sector
( 63)
x no. per sector
( 512)
1 Gigabyte
If user set his HDD to NORMAL mode, the maximum accessible
HDD size will be 528 Megabytes even though its physical size may
be greater than that!
To support LBA or LARGE mode of HDDs, there must be some
software involved. All these software are located in the Award HDD
Service Routine(INT 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.
3. Remarks
