Intel 460GX manual 3.4 I/O xAPIC RTE 10h-8Fh, I/O xAPIC Arbitration ID Register Format

Register Descriptions

Table 2-9. I/O (x)APIC Arbitration ID Register Format

Register Offset: 02h		Default Value: [00000000h]Attribute: Read-Only
Bit(s)	Name	Description
31:28	Reserved	These four bits are reserved.
27:24	ARBID	APIC Arbitration ID.
23:0	Reserved	These 24 bits are reserved.

2.6.3.4I/O (x)APIC RTE (10h-8Fh)

The interrupt RT has a dedicated entry for each interrupt input pin. Software can individually choose the interrupt vector number for input pins. For each individual pin, the operating system can also specify the signal polarity (low-active or high-active), whether the interrupt is signaled as edges or levels, as well as the destination and delivery mode of the interrupt. The information in the RT is used to generate the inter-(x)APIC message upon assertion/deassertion of the interrupt pin. The PID’s version register contains the number of entries in the interrupt RT. Offsets 10h through 8Fh are used for the interrupt RT. Each entry in the table is 64-bits. The format of each entry is described in Table 2-10.

Note: The interrupt RT is shared between SAPIC and APIC modes. Some of the fields have different meanings in the two modes as indicated in Columns 2 and 3. The PID implements only those bits that have valid functional fields associated with them. Reserved bits cannot be written and will return 0s when read.

Since each RTE is 64 bits wide, it must be accessed using two 32-bit memory read or write operations to consecutive dword-aligned addresses. The lower half of the entry, bits 31 through 0, is located at the even offset (such as 10h) and the upper half of the entry, bits 63 through 32, is located at the odd offset (such as 11h). While programming the RTEs, it is recommended that the lower half be programmed first, followed by the upper half.

Table 2-10. I/O (x)APIC RTE Format

Register Offset: 10-8Fh		Default Value: Undefined except mask bit is 1Attribute: Read/Write
Bit(s)	SAPIC Mode	APIC Mode	Description
	Name	Name
63:56	DEST ID	DEST ID	This field contains an (x)APIC ID. Local (x)APIC units receiving an interrupt
			message compare the DEST ID and DEST EID fields to the corresponding
			fields in their LID registers to determine if the interrupt is to be serviced by
			them.
55:48	DEST EID	Reserved	This field contains the extended (x)APIC ID. Local (x)APIC units receiving an
			interrupt message will use this field along with the DEST ID field to determine if
			the interrupt is to be accepted by them. This field is not used during APIC
			mode.
47:32	Reserved	Reserved	These 16 bits are reserved
31:18	Reserved	Reserved	These 14 bits are reserved
17	FLUSHEN	FLUSHEN	This bit controls the flushing of the I/O buffer on a per-interrupt basis.
			A 0 indicates that the buffer must be flushed before the interrupt is sent to the
			local (x)APIC. This setting will cause the hardware flush control signals to be
			used.
			A 1 indicates that the buffer does not need to be flushed before the interrupt is
			sent out to the local (x)APIC. This setting will cause the hardware flush control
			signals to be ignored.

2-50 Intel® 460GX Chipset Software Developer’s Manual