Intel MultiProcessor manual Bus Entries, 5.Bus Entry -7.Bus Entry Fields

MultiProcessor Specification

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.

31	24	23	16		15	8	7	0
			BUS TYPE STRING
					BUS ID			ENTRY TYPE
								1
31	24	23	16		15	8	7	0

04H

00H

Figure 4-5. Bus Entry

Table 4-7. Bus Entry Fields

	Offset	Length
Field	(in bytes)	(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	2	48	A string that identifies the type of bus. Refer to Table 4-8 for
STRING			values. These are 6-character ASCII (blank-filled) strings
			used by the MP specification.

4-10 Version 1.4