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MultiProcessor Specification
4-24 Version 1.4
Table 4-16. Compatibility Bus Address Space Modifier Entry Fields
Field
Offset
(in
bytes:bits)
Length
(in bits) Description
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.