IBM Aptiva Series Handbook page 64

Type
This item specifies the number of cylinders, heads, and
sectors, and the size of a particular IDE drive. If no
information appears opposite the parameters, there is no
drive installed in that channel.
Hard disk block mode
This function enhances disk performance depending on the
hard disk in use. BIOS automatically detects if your hard disk
supports this feature.
The Auto setting allows data transfer in blocks (multiple
sectors) to increase the data transfer rate. If your system
does not boot after setting this parameter to Auto, change
the setting to Disabled. The default setting for this parameter
is Auto.
Advanced PIO mode
The advanced PIO mode feature improves system
performance by allowing the use of faster hard disk drives. If
your hard disk supports this feature, you may set this
parameter to Auto (default), Mode 0, Mode 1, Mode 2, Mode
3, or Mode 4 depending on the hard disk requirements. See
the documentation that came with the hard disk.
5-8 Chapter 5: BIOS Setup configuration
Hard disk size > 504MB
This enhanced IDE feature works only under DOS and
Windows environments. If set to Auto, which is the default,
BIOS allows you to use a hard disk with a capacity of more
than 504MB. This is made possible through the Logical
Block Address (LBA) mode translation. You may be required
to set this parameter to Disabled if you use other operating
systems.
To prevent data loss, set this parameter to Auto if you are
using a hard disk with more than 504MB capacity that was
previously configured through the LBA mode. If you use a
hard disk configured through the user-specific Cylinder-
Head-Sector (CHS) mode, set this parameter to Disabled.
Hard disk 32-bit access
Setting this parameter to Enabled improves system
performance by allowing the use of the 32-bit hard disk
access. This enhanced IDE feature only works under DOS,
Windows 3.x, Windows 95, and Novell NetWare. If your
software does not support this function, set this parameter to
Disabled. The default setting is Enabled.