QDI P4I865G User Manual page 35

C h a p t e r C h a p t e r C h a p t e r 3 3 3
C h a p t e r C h a p t e r 3 3
The Award BIOS supports 3 HDD modes: NORMAL, LBA and LARGE,or Auto
detect.
CHS mode
Generic access mode in which neither the BIOS nor the IDE controller will make
any transformation during accessing. The maximum number of cylinders, heads
and sectors for CHS mode are 1024,16 and 63.
If the user sets his 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 and 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 and cylinder number into its own physical address
inside the HDD.
Large mode
Some IDE HDDs contain more than 1024 cylinder without LBA support (in some
cases, users do not want LBA). The Award BIOS provides another alternative to
support these kinds of HDD.
BIOS tricks DOS (or other OS) into divising the number of cylinders is less than
1024 by dividing it by 2. At the same time, the number of heads is multiplied by
2. A reverse transformation process will be made inside INT13h in order to
access the right HDD address.
Auto Detect
If using Auto detect, the BIOS will automatically detect the IDE hard disk mode
and set it as one of the three modes.
Remark
To support LBA or LARGE mode of HDDs, there must be some softwares in-
volved which are located in Award HDD Service Routine(INT13h).It may fail to
access a HDD with LBA (LARGE) mode selected if you are running under an
Operating System which replaces the whole INT 13h.
P4I865G/P/PEA User'S Manual
BIOS Description BIOS Description
BIOS Description BIOS Description BIOS Description
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