Advanced Configuration and Power Interface Specification

Processor Configuration and Control
platform might notify OSPM that the number of supported C States has changed as a result of an
asynchronous AC insertion / removal event.
The platform must specify unique C_State_Register addresses for all entries within a given _CST
object.
_CST eliminates the ACPI 1.0 restriction that all processors must have C State parity. With _CST,
each processor can have its own characteristics independent of other processors. For example,
processor 0 can support C1, C2 and C3, while processor 1 supports only C1.
The fields in the processor structure remain for backward compatibility.
Example
Processor (
\_SB.CPU0, // Processor Name
1, // ACPI Processor number
0x120, // PBlk system IO address
6 ) // PBlkLen
{
Name(_CST, Package()
{
4, // There are four C-states defined here with three semantics
// The third and fourth C-states defined have the same C3 entry semantics
Package(){ResourceTemplate(){Register(FFixedHW, 0, 0, 0)}, 1, 20, 1000},
Package(){ResourceTemplate(){Register(SystemIO, 8, 0, 0x161)}, 2, 40, 750},
Package(){ResourceTemplate(){Register(SystemIO, 8, 0, 0x162)}, 3, 60, 500},
Package(){ResourceTemplate(){Register(SystemIO, 8, 0, 0x163)}, 3, 100, 250}
})
}
Notice in the example above that OSPM should anticipate the possibility of a _CST object providing
more than one entry with the same C_State_Type value. In this case OSPM must decide which
C_State_Register it will use to enter that C state.
Example
This is an example usage of the _CST object using the typical values as defined in ACPI 1.0.
Processor (
\_SB.CPU0, // Processor Name
1, // ACPI Processor number
0x120, // PBLK system IO address
6 ) // PBLK Len
{
Name(_CST, Package()
{
2, // There are two C-states defined here – C2 and C3
Package(){ResourceTemplate(){Register(SystemIO, 8, 0, 0x124)}, 2, 2, 750},
Package(){ResourceTemplate(){Register(SystemIO, 8, 0, 0x125)}, 3, 65, 500}
})
}
The platform will issue a Notify(\_SB.CPU0, 0x81) to inform OSPM to re-evaluate this object when
the number of available processor power states changes.
Version 6.0 431