Advanced Configuration and Power Interface Specification

ACPI Software Programming Model
• System Resource Affinity Table (SRAT)
• Corrected Platform Error Polling Table (CPEP)
• Maximum System Characteristics Table (MSCT)
• ACPI RAS FeatureTable (RASF)
• Memory Power StateTable (MPST)
• Platform Memory Topology Table (PMTT)
• Boot Graphics Resource Table (BGRT)
• Firmware Performance Data Table (FPDT)
• Generic Timer Description Table (GTDT)
• NVDIMM Firmware Interface Table (NFIT)
All numeric values in ACPI-defined tables, blocks, and structures are always encoded in little endian
format. Signature values are stored as fixed-length strings.
5.2.1 Reserved Bits and Fields
For future expansion, all data items marked as reserved in this specification have strict meanings.
This section lists software requirements for reserved fields. Notice that the list contains terms such
as ACPI tables and AML code defined later in this section of the specification.
5.2.1.1 Reserved Bits and Software Components
• OEM implementations of software and AML code return the bit value of 0 for all reserved bits
in ACPI tables or in other software values, such as resource descriptors.
• For all reserved bits in ACPI tables and registers, OSPM implementations must:
• Ignore all reserved bits that are read.
• Preserve reserved bit values of read/write data items (for example, OSPM writes back reserved
bit values it reads).
• Write zeros to reserved bits in write-only data items.
5.2.1.2 Reserved Values and Software Components
• OEM implementations of software and AML code return only defined values and do not return
reserved values.
• OSPM implementations write only defined values and do not write reserved values.
5.2.1.3 Reserved Hardware Bits and Software Components
• Software ignores all reserved bits read from hardware enable or status registers.
• Software writes zero to all reserved bits in hardware enable registers.
• Software ignores all reserved bits read from hardware control and status registers.
• Software preserves the value of all reserved bits in hardware control registers by writing back
read values.
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