Intel MultiProcessor Specification page 91

information byte 2, the IMCR present bit, is used by the operating system to determine whether
PIC Mode or Virtual Wire Mode is implemented by the system.
The physical address pointer field contains the address of the beginning of the MP configuration
table. If it is nonzero, the MP configuration table can be accessed at the physical address provided
in the pointer structure. This field must be all zeros if the MP configuration table does not exist.
4.4.1 System Address Space Mapping Entries
System Address Space Mapping entries define the system addresses that are visible on a particular
bus. Each bus defined in the Base Table can have any number of System Address Space Mapping
entries included in the Extended Table. Thus, individual buses can be configured to support
different address ranges, thereby decreasing the amount of bus traffic on a given bus and increasing
the overall system performance. Each consecutive address range that is usable by the operating
system to access devices on a given bus has a System Address Space Mapping entry. Figure 4-9
shows the format of each entry, and Table 4-14 explains each field.
31
31
Version 1.4
28 27 24 23 20 19
ADDRESS LENGTH
ADDRESS BASE
ADDRESS TYPE BUS ID
28 27 24 23 20 19
Figure 4-9. System Address Space Entry
16 15 12 11 8 7 4 3
ENTRY TYPE
ENTRY LENGTH
128
16 15 12 11 8 7 4 3
MP Configuration Table
0
10H
0CH
08H
04H
00H
0
E-3