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Version 1.4 5-1
5
Default Configurations
The MP specification defines several default MP system configurations. The purpose of these
defaults is to simplify BIOS design. If a system conforms to one of the default configurations, the
BIOS will not need to provide the MP configuration table. The operating system will have the
default MP configuration table predefined internally.
Default system configuration types are defined by MP feature information byte 1, which is part of
the MP floating pointer structure. The physical address pointer field of the MP floating pointer
structure must be zero if one of the default configurations is selected. (Refer to Chapter 4 for a
detailed description of the MP floating pointer structure.)
To use a default configuration, a system must meet the following basic criteria:
1. The system supports two processors.
2. Both processors must execute the common Intel architecture instruction set.
3. The local APICs are located at base memory address 0FEE0_0000h.
4. The local APIC IDs are assigned consecutively by hardware starting from zero.
5. An I/O APIC is present at base memory address 0FEC0_0000h.
6. Either PIC Mode or Virtual Wire Mode is implemented as the power-on default interrupt
mode.
The default system configurations include configurations that use the discrete APIC, such as the
Intel 82489DX or its equivalent, and configurations that use the integrated APIC, such as the
Pentium processors (735\90, 815\100).
Each default configuration has a unique code. Table 5-1 specifies the configuration associated with
each code.