Field Name Bits Default Description
Smi_Gevent_En 12 0b Enable all the events with the capability of doing both SMI#
and SCI to SMI# assertion. If enabled, an assertion at any of
the event inputs will cause SMI# to be asserted if SCI EN is
not set.
0 – Disable
1 – Enable
Intr_block_En 13 0b Applicable in the PIC system. When enabled, it will block any
pending interrupt for approximately 500ns after IntrAck cycle
from the host.
0 – Disable
1 – Enable
ApicPort02Swap 14 0b When set, port 0 of APIC is connected to output of the PIC and
port 2 is connected to IRQ0 (timer0)
When clear, port 0 of APIC is connected to IRQ0 (timer0) and
port 2 is connected to the output of the PIC. Software should
set this bit to conform with MP spec.
UsbSmiEn 15 0b USB SMI# enable:
1 = Enable
0 = Disable
Serr2Smi_En 16 0b Enable SERR# to SMI# assertion
0 – Disable
1 – Enable
Gevent1_en0 17 0b GEVENT group 0 enable (GPM[7] to SMI#/SCI enable) to
ACPI function
Gevent1_en1 18 0b GEVENT group 1 enable (GPM[6] to SMI#/SCI enable) to
ACPI function
Gevent1_en2 19 0b GEVENT group 2 enable (GPM[5:4] to SMI#/SCI enable) to
ACPI function
LpcEnable 20 0b 1 – Enable lpc controller
0 – Disable lpc controller
RtcSelect 21 0b Writing this bit with 1 will toggle the selection between Internal
RTC and External RTC which is set via strap bit.
Reading this bit returns the internal/external mode:
1 = External RTC
0 = Internal RTC
Gevent1_en3 22 0b GEVENT group 3 enable (ExtEvent[1:0], PCIePme) to ACPI
function
Gevent1_en4 23 0b GEVENT group 4 enable (GPM[3:0]) to ACPI function
Reserved 24
DmaVerifyEn 25 0b With LPC is replacing the ISA bus, software needs to set this
bit in order to for DMA verify to work properly
IRQ1MergeEn 26 0b This is the old method to merge the normal IRQ1 with the USB
legacy IRQ1 function. Since this is no longer needed, software
should always leave this bit with 0.
IRQ12MergeEn 27 0b This is the old method to merge the normal IRQ12 with the
USB legacy IRQ12 function. Since this is no longer needed,
software should always leave this bit with 0.
SB_ClkStpEn 29:28 00b SB_ClkStpEn[0] enables PciStpB to stop primary PCI clock.
SB_ClkStpEn[1] enables PciStpB to stop secondary PCI clock
UsbA20En 30 0b USB A20 enable
UsbLegacyIrqEn 31 0b Enable for IRQ1/12 from USB (BIOS should always set it to 1)
Features Enable register
UsbEnable - RW - 8 bits - [PCI_Reg: 68h] Field Name Bits Default Description
EHCI_enable 0 1b Set to 1 to enable EHCI
OHCI_0_enable 1 1b Set to 1 to enable OHCI_0
OHCI_1_enable 2 1b Set to 1 to enable OHCI_1