Major Chips Description 2-25
Table 2-282371AB Pin Descriptions
Name Type Description
GENERAL PURPOSE INPUT AND OUTPUT SIGNALS
Some of the General Purpose Input and Output signals are multiplexed with other PIIX4 signals. The usage
is determined by the system configuration. The default pin usage is shown in Table 1 and Table 2. The
configuration can be selected via the General Configuration register and X-Bus Chip Select register.
GPI[21:0] IGENERAL PURPOSE INPUTS. These input signals can be monitored via the
GPIREG register located in Function 3 (Power Management) System IO Space
at address PMBase+30h. See Table 1 for details.
GPO[30:0] OGENERAL PURPOSE OUTPUTS. These output signals can be controlled via the
GPIREG register located in Function 3 (Power Management) System IO Space
at address PMBase+34h.
If a GPO pin is not multiplexed with another signal or defaults to GPO, then its
state after reset is the reset condition of the GPOREG register. If the GPO
defaults to another signal, then it defaults to that signal’s state after reset. The
GPO pins that default to GPO remain stable after reset. The others may toggle
due to system boot or power control sequencing after reset prior to their being
programmed as GPOs. The GPO8 signal is driven low upon removal of power
from the PIIX4 core power plane. All other GPO signals are invalid (buffers
powered off).
GPI SIGNALS
Signal
Name Multiplexed
With Default Control Register
and Bit (PCI
Function 1)
Notes
GPI0 IOCHK# GPI GENCFG
Bit 0 Available as GPI only if in EIO bus mode.
GPI1# GPI Non-multiplexed GPI which is always available. This
signal when used by power management logic is
active low.
GPI[2:4] REQ[A:C]# GPI GENCFG
Bits 8–10 Not available as GPI if used for PC/PCI. Can be
individually enabled, so for instance, GPI[4] is
available if REQ[C]# is not used.
GPI5 APICREQ# GPI XBCS
Bit 8 Not available as GPI if using an external APIC.
GPI6 IRQ8# GPI GENCFG
Bit 14 Not available as GPI if using external RTC or
external APIC.
GPI7 SERIRQ GPI GENCFG
Bit 16 Not available as GPI if using Serial IRQ protocol.
GPI8 THRM# THRM# GENCFG
Bit 23 Not available as GPI if using thermal monitoring.
GPI9 BATLOW# BATLOW# GENCFG
Bit 24 Not available as GPI if using battery low feature.
GPI10 LID# LID GENCFG
Bit 25 Not available as GPI if using LID feature.
GPI11 SMBALERT# SMBALERT# GENCFG
Bit 15 Not available as GPI if using SMBALERT feature
GPI12 RI# RI# GENCFG
Bit 27 Not available if using ring indicator feature
GPI[13:21] GPI Non-multiplexed GPIs which are always available.