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MultiProcessor Specification
4-6 Version 1.4
Table 4-2. MP Configuration Table Header Fields
Field
Offset
(in bytes)
Length
(in bits) Description
SIGNATURE 0 32 The ASCII string representation of “PCMP,” which
confirms the presence of the table.
BASE TABLE LENGTH 4 16 The length of the base configuration table in bytes,
including the header, starting from offset 0. This field
aids in calculation of the checksum.
SPEC_REV 6 8 The version number of the MP specification. A value
of 01h indicates Version 1.1. A value of 04h indicates
Version 1.4.
CHECKSUM 7 8 A checksum of the entire base configuration table. All
bytes, including CHECKSUM and reserved bytes,
must add up to zero.
OEM ID 8 64 A string that identifies the manufacturer of the system
hardware.
PRODUCT ID 16 96 A string that identifies the product family.
OEM TABLE POINTER 28 32 A physical-address pointer to an OEM-defined
configuration table. This table is optional. If not
present, this field is zero.
OEM TABLE SIZE 32 16 The size of the base OEM table in bytes. If the table
is not present, this field is zero.
ENTRY COUNT 34 16 The number of entries in the variable portion of the
base table. This field helps the software identify the
end of the table when stepping through the entries.
ADDRESS OF LOCAL APIC 36 32 The base address by which each processor accesses
its local APIC.
EXTENDED TABLE
LENGTH
40 16 Length in bytes of the extended entries that are
located in memory at the end of the base
configuration table. A zero value in this field indicates
that no extended entries are present.
EXTENDED TABLE
CHECKSUM
42 8 Checksum for the set of extended table entries,
including only extended entries starting from the end
of the base configuration table. When no extended
table is present, this field is zero.
4.3 Base MP Configuration Table Entries
A variable number of variable length entries follow the header of the MP configuration table. The
first byte of each entry identifies the entry type. Each entry type has a known, fixed length. The
total length of the MP configuration table depends upon the configuration of the system. Software
must step through each entry in the base table
until it reaches ENTRY COUNT. The entries are
sorted on ENTRY TYPE in ascending order. Table 4-3 gives the meaning of each value of
ENTRY TYPE.