82378ZB Datasheet, PDF (82/137 Pages) Intel Corporation – SYSTEM I/O APIC(SIO.A) AND

82378ZB (SIO) AND 82379AB (SIO.A)
E
3.7.1. IOREGSEL—I/O REGISTER SELECT REGISTER (82379AB Only)
Memory Address:
Default Value:
Attribute:
FEC0 xy00h (xy=See APICBASE Register)
00h
Read/Write
This register selects an I/O APIC Unit register. The contents of the selected 32-bit register can be manipulated
via the I/O Window Register.
Bit
Description
31:8 Reserved
7:0 APIC Register Address: Bits[7:0] specify the APIC register to be read/written via the IOWIN Register.
3.7.2. IOWIN—I/O WINDOW REGISTER (82379AB Only)
Memory Address:
Default Value:
Attribute:
FEC0 xy10h (xy=See APICBASE Register)
00h
Read/Write
This register is mapped onto the I/O Unit's register selected by the IOREGSEL Register. Readability/writability
by software is determined by the I/O APIC register that is currently selected.
Bit
Description
31:0 APIC Register Data: Memory references to this register are mapped to the APIC register specified
by the contents of the IOREGSEL Register.
3.7.3. APICID—I/O APIC IDENTIFICATION REGISTER (82379AB Only)
Address Offset:
Default Value:
Attribute:
00h
00000000h
Read/Write
This register contains the unit's 4-bit APIC ID. The ID serves as a physical name of the I/O APIC Unit. All APIC
units using the APIC Bus should have a unique APIC ID. The APIC Bus arbitration ID for the I/O unit is also
writtten during a write to the APICID Register (same data is loaded into both). This register must be programmed
with the correct ID value before using the I/O APIC unit for message transmission.
Bit
Description
31:28 Reserved
27:24 I/O APIC Identification: This 4 bit field contains the I/O APIC identification.
23:0 Reserved
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