Advanced Configuration and Power Interface Specification

Device Configuration
Offset Field Name Definition
Byte 54 Type Specific Attribute,
_ATT bits[55:48]
Byte 55 Type Specific Attribute,
_ATT bits[63:56]
See Section 19.5.43, “ExtendedSpace (Extended Address Space Resource Descriptor Macro),” for a
description of the ASL macro that creates an Extended Address Space descriptor.
6.4.3.5.4.1 Type Specific Attributes
The meaning of the Type Specific Attributes field of the Extended Address Space Descriptor
depends on the value of the Resource Type field in the descriptor. When Resource Type = 0
(memory resource), the Type Specific Attributes field values are defined as follows:
// These attributes can be "ORed" together as needed.
#define ACPI_MEMORY_UC 0x0000000000000001
#define ACPI_MEMORY_WC 0x0000000000000002
#define ACPI_MEMORY_WT 0x0000000000000004
#define ACPI_MEMORY_WB 0x0000000000000008
#define ACPI_MEMORY_UCE 0x0000000000000010
#define ACPI_MEMORY_NV 0x0000000000008000
ACPI_MEMORY_UC – Memory cacheability attribute. The memory region supports being
configured as not cacheable.
ACPI_MEMORY_WC – Memory cacheability attribute. The memory region supports being
configured as write combining.
ACPI_MEMORY_WT – Memory cacheability attribute. The memory region supports being
configured as cacheable with a "write through "policy. Writes that hit in the cache will also be
written to main memory.
ACPI_MEMORY_WB – Memory cacheability attribute. The memory region supports being
configured as cacheable with a "write back "policy. Reads and writes that hit in the cache do not
propagate to main memory. Dirty data is written back to main memory when a new cache line is
allocated.
ACPI_MEMORY_UCE – Memory cacheability attribute. The memory region supports being
configured as not cacheable, exported, and supports the "fetch and add "semaphore mechanism.
ACPI_MEMORY_NV – Memory non-volatile attribute. The memory region is non-volatile. Use of
memory with this attribute is subject to characterization.
Note: These bits are defined so as to match the UEFI definition when applicable.
6.4.3.5.5 Resource Type Specific Flags
The meaning of the flags in the Type Specific Flags field of the Address Space Descriptors depends
on the value of the Resource Type field in the descriptor. The flags for each resource type are
defined in the following tables:
332 Hewlett-Packard/Intel/Microsoft/Phoenix/Toshiba