MP Configuration Table
4.4Extended MP Configuration Table Entries
A variable number of
∙ENTRY TYPE
∙ENTRY LENGTH
∙DATA
ENTRY TYPE and ENTRY LENGTH make up a header that is present in all extended configuration table entries. The ENTRY TYPE and ENTRY LENGTH fields are eight bit unsigned values. ENTRY LENGTH specifies the total length of the given configuration entry. The length of the DATA field is two bytes less than the value specified by ENTRY LENGTH.
This scheme ensures that operating systems can parse all the entries in the extended MP configuration table area, even if an entry type is unrecognized. Operating systems that find an unknown entry type when parsing this section of the table should ignore the content and move on to the next entry, until the offset from the end of the base table reaches the length that is specified in the EXTENDED TABLE LENGTH field of the configuration table header. The ability to skip entries with unrecognized type codes beyond those listed in Table
The total length of the Extended MP configuration table depends upon the configuration of the system. The entries are sorted on ENTRY TYPE in ascending order. Table
Table 4-13. Extended MP Configuration Table Entry Types
| Entry Type | Length |
|
Entry Description | Code* | (in bytes) | Comments |
|
|
|
|
SYSTEM ADDRESS SPACE | 128 | 20 | Entry to declare system visible memory |
MAPPING |
|
| or I/O space on a bus. |
|
|
|
|
BUS HIERARCHY DESCRIPTOR | 129 | 8 | Entry to describe I/O bus interconnection. |
|
|
|
|
COMPATIBILITY BUS ADDRESS | 130 | 8 | Entry to describe predefined address |
SPACE MODIFIER |
|
| ranges that modify the memory or I/O |
|
|
| space visible on a bus in order to support |
|
|
| ISA compatibility. |
|
|
|
|
*All other type codes are reserved.
Version 1.4 |
