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Theory of Operation
Table 2 illustrates the valid values that system BIOS can use for the programming interface
register when in enhanced mode.
Note: The ICH5 does permit the SATA and P-ATA host controllers to simultaneously operate in native
mode if they are programmed to do so by the operating system. Due to potential operating system
incompatibilities, it is a requirement (when in enhanced mode) that the system BIOS programs the
P-ATA and SATA host controllers exactly as described in Table 2.
Caution: Improper programming could result in undefined behavior.
Some Microsoft operating systems have specific platform support requirements when operating on
systems capable of native mode of operation. Refer to paper titled BIOS Settings for Native-Mode-
Capable ATA Controllers, available from Microsoft Corporation at:
http://www.microsoft.com/hwdev/storage/, for additional operating system-related details.
Table 2. Valid BIOS Option for the Programming Interface Register
POP_MODE_SEL
Note: The SATA and P-ATA host controllers do not support the programming of the primary and
secondary channels differently (i.e., primary as native and secondary as legacy). Programming the
controllers with values other than those specified above is illegal and will result in undefined
hardware behavior.
Table 3 illustrates an illegal programming combination. System BIOS programming of all the
channels (both the SATA and P-ATA controllers) for legacy mode or native will result in
undefined behavior. Operating system software requiring legacy only mode capability is required
to find the SATA host controller configured for compatible mode.
Table 3. Illegal BIOS Options for the Programming Interface Register
POP_MODE_SEL
Note: Following a reset, the SATA and P-ATA controllers will both be configured for legacy mode.
Therefore it is very important that system BIOS program these registers with legal values as
defined in Table 2. Valid BIOS Option for the Programming Interface Register
22
SATA – Device 31, Function 2
SOP_MODE_SEL
1
1
SATA – Device 31, Function 2
SOP_MODE_SEL
0
0
0
0
1
1
P-ATA – Device 31, Function 1
POP_MODE_SEL
0
P-ATA – Device 31, Function 1
_ SOP_MODE_SEL
0
1
1
SATA Programmer's Reference Manual
R
SOP_MODE_SEL
0
SOP_MODE_SEL
0
1
1
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