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ATAPI unit type
Option Description Note
None (*) No unit selected Default setting for both
ATAPI Units (Master1 &
Slave1)
(*) = Default setting
Auto Unit auto-detection
LBA LBA unit selected
CHS CHS unit selected
CD-ROM CD-ROM unit selected
Other Other unit selected
Note: when the Auto feature is selected, the BIOS ignores any other data (like Mode, Cyls,
Head, etc.). Use this option for the most of hard disks or other ATAPI devices.
Note: LBA and CHS are two different types of ATAPI units addressing mode. The first one is
normally used with modern hard disk, from 512 Kbytes to above 8 Gbytes. For both modes
you have to know the physical hard-disk structure in terms of Cylinders, Heads and Sectors.
So, for an easy use of any kind of disk, the Auto option is preferable.
Note: to speed-up the bootstrap select the option None for unused ATAPI devices.
PIO Mode
PIO is a special data-transfer system between two or more EIDE devices, where all the data pass
through the processor. There are five transfer rates, called PIO mode n (with n=0..4). If the Auto
(autodetect) option is disabled, the PIO mode must be specified.
Option Description Note
PIO-0 Transfer Rate of 3.3 MBps
PIO-1 Transfer Rate of 5.2 MBps
PIO-2 Transfer Rate of 8.3 MBps
PIO-3 Transfer Rate of 11.1 MBps
PIO-4 (*) Transfer Rate of 16.6 MBps Default setting for both
ATAPI Units (Master1 &
Slave1)
(*) = Default setting