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MP Configuration Table
Version 1.4 4-7
Table 4-3. Base MP Configuration Table Entry Types
Entry Description Entry Type Code*
Length
(in bytes) Comments
Processor 0 20 One entry per processor.
Bus 1 8 One entry per bus.
I/O APIC 2 8 One entry per I/O APIC.
I/O Interrupt Assignment 3 8 One entry per bus interrupt source.
Local Interrupt Assignment 4 8 One entry per system interrupt
source.
* All other type codes are reserved.
4.3.1 Processor Entries
Figure 4-4 shows the format of each processor entry, and Table 4-4 defines the fields.
RESERVED
RESERVED
31 0374811121516192023242728
CPU SIGNATURE
LOCAL APIC ID
CPU FLAGS
FEATURE FLAGS
31 0374811121516192023242728
00H
04H
08H
0CH
10H
LOCAL APIC
VERSION #
ENTRY TYPE
0
E
N
RESERVED
B
P
Figure 4-4. Processor Entry
In systems that use the MP configuration table, the only restriction placed on the assignment of
APIC IDs is that they be unique
. They do not need to be consecutive. For example, it is possible
for only APIC IDs 0, 2, and 4 to be present.