31:8

0h

RO

Reserved

7

0h

RW

ACPI Enable (EN)

When set, decode of the I/O range pointed to by the ACPI base register is enabled and the ACPI power management function is enabled.

6:3

0h

RO

Reserved

2:0

0h

RW

SCI IRQ Select (SCIS)

Specifies on which IRQ the SCI will internally appear. If not using the APIC, the SCI must be routed to IRQ[9-11], and that interrupt is not sharable with the SERIRQ stream, but is shareable with other PCI interrupts. If using the APIC, the SCI can also be mapped to IRQ20-23, and can be shared with other interrupts.
Bits - SCI Map
---- - -------
000 - IRQ9
001 - IRQ10
010 - IRQ11
011 - Reserved
100 - IRQ20 (only if APIC is enabled)
101 - IRQ21 (only if APIC is enabled)
110 - IRQ22 (only if APIC is enabled)
111 - IRQ23 (only if APIC is enabled)
When the interrupt is mapped to APIC interrupts 9, 10 or 11, the APIC should be programmed for active-high reception. When the interrupt is mapped to APIC interrupts 20 through 23, the APIC should be programmed for active-low reception.