Intel 64 and IA-32 Architectures Software Developers Manual Volume 3B, System Programming Guide Part 2

Table Of Contents
Vol. 3 F-3
APIC BUS MESSAGE FORMATS
If the physical delivery mode is being used, then cycles 15 and 16 represent the APIC
ID and cycles 13 and 14 are considered don't care by the receiver. If the logical
delivery mode is being used, then cycles 13 through 16 are the 8-bit logical destina-
tion field.
For shorthands of “all-incl-self” and “all-excl-self,” the physical delivery mode and an
arbitration priority of 15 (D0:D3 = 1111) are used. The agent sending the message
is the only one required to distinguish between the two cases. It does so using
internal information.
When using lowest priority delivery with an existing focus processor, the focus
processor identifies itself by driving 10 during cycle 19 and accepts the interrupt.
This is an indication to other APICs to terminate arbitration. If the focus processor
has not been found, the short message is extended on-the-fly to the non-focused
lowest-priority message. Note that except for the EOI message, messages gener-
ating a checksum or an acceptance error (see Section 9.6.3, “Error Handling”) termi-
nate after cycle 21.
F.2.2 Non-focused Lowest Priority Message
These 34-cycle messages (see Table F-3) are used in the lowest priority delivery
mode when a focus processor is not present. Cycles 1 through 20 are same as for the
short message. If during the status cycle (cycle 19) the state of the (A:A) flags is
10B, a focus processor has been identified, and the short message format is used
(see Table F-2). If the (A:A) flags are set to 00B, lowest priority arbitration is started
and the 34-cycles of the non-focused lowest priority message are competed. For
other combinations of status flags, refer to Section F.2.3, “APIC Bus Status Cycles.
Table F-3. Non-Focused Lowest Priority Message (34 Cycles)
Cycle Bit0 Bit1
10 10 1 = normal
2 ArbID3 0 Arbitration ID bits 3 through 0
3ArbID20
4ArbID10
5ArbID00
6 DM M2 DM = Destination mode
7M1M0M2-M0 = Delivery mode
8 L TM L = Level, TM = Trigger Mode
9 V7 V6 V7-V0 = Interrupt Vector
10 V5 V4
11 V3 V2
12 V1 V0