
Register and Memory Mapping
6-6
82801AA and 82801AB Datasheet
6.2.2
Variable I/O Decode Ranges
Table 6-4
shows the Variable I/O Decode Ranges. They are set using Base Address Registers
(BARs) or other configuration bits in the various PCI configuration spaces. The PNP software (PCI
or ACPI) can use their configuration mechanisms to set and adjust these values.
When a cycle is detected on hub interface, the ICH will positively decode the cycle. If the response
is on the behalf of an LPC device, ICH forwards the cycle to the LPC interface.
Refer to
Table A-3
for a complete list of all variable I/O registers.
Warning:
The Variable I/O Ranges should not be set to conflict with the Fixed I/O Ranges. Unpredictable
results if the configuration software allows conflicts to occur. The ICH does not perform any
checks for conflicts.
Table 6-4. Variable I/O Decode Ranges
Range Name
Mappable
Size (Bytes)
Target
ACPI
Anywhere in 64K I/O Space
64
Power Management
IDE
Anywhere in 64K I/O Space
16
IDE Unit
USB
Anywhere in 64K I/O Space
32
USB Unit
SMBus
Anywhere in 64K I/O Space
16
SMB Unit
AC’97 Audio Mixer
Anywhere in 64K I/O Space
256
AC’97 Unit
AC’97 Bus Master
Anywhere in 64K I/O Space
64
AC’97 Unit
AC’97 Modem Mixer
Anywhere in 64K I/O Space
256
AC’97 Unit
TCO
96 Bytes above ACPI Base
32
TCO Unit
GPIO
Anywhere in 64K I/O Space
64
GPIO Unit
Parallel Port
3 ranges in 64K I/O Space
8
LPC Peripheral
Serial Port 1
8 Ranges in 64K I/O Space
8
LPC Peripheral
Serial Port 2
8 Ranges in 64K I/O Space
8
LPC Peripheral
Floppy Disk Controller
2 Ranges in 64K I/O Space
8
LPC Peripheral
MIDI
4 Ranges in 64K I/O Space
2
LPC Peripheral
MSS
4 Ranges in 64K I/O Space
8
LPC Peripheral
SoundBlaster
2 Ranges in 64K I/O Space
32
LPC Peripheral
AdLib
2 Ranges in 64K I/O Space
2
LPC Peripheral
LPC Generic 1
Anywhere in 64K I/O Space
128 bytes (with mask)
LPC Peripheral
LPC Generic 2
Anywhere in 64K I/O Space
16 bytes (with mask)
LPC Peripheral