Intel MultiProcessor manual Compatibility Bus Address Space Modifier Entry Fields

MultiProcessor Specification

Table 4-16. Compatibility Bus Address Space Modifier Entry Fields

	Offset	Length
Field	(in	(in bits)	Description
	bytes:bits)
ENTRY TYPE	0	8	Entry type 130 identifies a Compatibility Bus
			Address Space Modifier Entry.
ENTRY LENGTH	1	8	A value of 8 indicates that an entry of this type is
			eight bytes long.
BUS ID	2	8	Bus for address space mappings are to be
			modified. This number corresponds to the BUS
			ID as defined in the base table entry for this bus.
ADDRESS MODIFIER:PR	3:0	1	If this bit is set to one, the address ranges
			specified by PREDEFINED RANGE LIST are to
			be subtracted from the address space
			associated with the bus. If this bit is set to zero,
			the specified address ranges are to be added to
			the address space associated with the bus.
PREDEFINED RANGE LIST	4	32	A number that indicates the list of predefined
			address space ranges that this record will
			modify for the bus.

PREDEFINED RANGE LIST may take one of the values from Table 4-17. The value of PREDEFINED RANGE LIST indicates the set of address ranges that are to be either added to or subtracted from the address range associated with the BUS ID.

Table 4-17. Predefined Range Lists

List	Value	Address Ranges
ISA Compatible I/O Range	0	X100-X3FF
		X500-X7FF
		X900-XBFF
		XD00-XFFF
VGA Compatible I/O Range	1	X3B0 - X3BB
		X3C0 - X3DF
		X7B0 - X7BB
		X7C0 - X7DF
		XBB0 - XBBB
		XBC0 - XBDF
		XFB0 - XFBB
		XFC0 - XFDF

All addresses in Table 4-17 are in hexadecimal notation. In each case the X represents any hexadecimal digit, 0-F. As a result, the ISA Compatible I/O Range describes 64 distinct ranges.

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