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MultiProcessor Specification
4-10 Version 1.4
4.3.2 Bus Entries
Bus entries identify the kinds of buses in the system. Because there may be more than one bus in a
system, each bus is assigned a unique bus ID number by the BIOS. The bus ID number is used by
the operating system to associate interrupt lines with specific buses. Figure 4-5 shows the format
of a bus entry, and Table 4-7 explains the fields of each entry.
00H
04H
31 07815162324
31 07815162324
ENTRY TYPE
1
BUS ID
BUS TYPE STRING
Figure 4-5. Bus Entry
Table 4-7. Bus Entry Fields
Field
Offset
(in bytes)
Length
(in bits) Description
ENTRY TYPE 0 8 Entry type 1 identifies a bus entry.
BUS ID 1 8 An integer that identifies the bus entry. The BIOS assigns
identifiers sequentially, starting at zero.
BUS TYPE
STRING
2 48 A string that identifies the type of bus. Refer to Table 4-8 for
values. These are 6-character ASCII (blank-filled) strings
used by the MP specification.