Intel MultiProcessor manual 126

MultiProcessor Specification

Table 4-1. MP Floating Pointer Structure Fields

	Offset	Length
Field	(in bytes:bits)	(in bits)	Description
SIGNATURE	0	32	The ASCII string represented by “_MP_” which
			serves as a search key for locating the pointer
			structure.
PHYSICAL ADDRESS	4	32	The address of the beginning of the MP
POINTER			configuration table. All zeros if the MP
			configuration table does not exist.
LENGTH	8	8	The length of the floating pointer structure table
			in paragraph (16-byte) units. The structure is 16
			bytes or 1 paragraph long; so this field contains
			01h.
SPEC_REV	9	8	The version number of the MP specification
			supported. A value of 01h indicates Version 1.1.
			A value of 04h indicates Version 1.4.
CHECKSUM	10	8	A checksum of the complete pointer structure.
			All bytes specified by the length field, including
			CHECKSUM and reserved bytes, must add up to
			zero.
MP FEATURE	11	8	Bits 0-7:MP System Configuration Type.
INFORMATION BYTE 1			When these bits are all zeros, the MP
			configuration table is present. When nonzero,

the value indicates which default configuration (as defined in Chapter 5) is implemented by the system.

MP FEATURE	12:0	6
INFORMATION BYTE 2	12:6	1

12:71

Bits 0-5:Reserved for future MP definitions.

Bit 6: Multiple Clock Sources. When set, this bit indicates that the processors derive clock signals from different sources. Otherwise when not set this bit indicates that all processors share a single clock source.

Bit 7: IMCRP. When the IMCR presence bit is set, the IMCR is present and PIC Mode is implemented; otherwise, Virtual Wire Mode is implemented.

MP FEATURE	13	24	Reserved for future MP definitions. Must be
INFORMATION BYTES 3-5			zero.

The MP feature information byte 1 specifies the MP system default configuration type. If nonzero, the system configuration conforms to one of the default configurations. The default configurations, specified in Chapter 5, may only be used to describe systems that always have two processors installed.

Bit 6 of MP feature information byte 2, the Multiple Clock Source bit, is used by the operating system to determine how processors derive clock sources. If the system design does not provide

for a single clock source shared by all processors then this bit is set. Otherwise this bit is zero to

indicate that all processors derive their clock from a common source. Bit 7 of MP feature

E-2 Version 1.4