Advanced Configuration and Power Interface Specification

Processor Configuration and Control
8.4.7.1.4 CPPC Enable Register
Optional
Register Location: System I/O, PCC, or Functional Fixed Hardware
Attribute:
Read/Write
Size:
>=1 bit(s)
If supported by the platform, OSPM writes a one to this register to enable CPPC on this processor.
If not implemented, OSPM assumes the platform always has CPPC enabled.
8.4.7.1.5 Autonomous Selection Enable Register
Optional
Register or DWORD
Register Location:System I/O, PCC, or Functional Fixed Hardware
Attribute: Read/Write
Size:
>=1 bit(s)
If supported by the platform, OSPM writes a one to this register to enable Autonomous Performance
Level Selection on this processor. CPPC must be enabled via the CPPC Enable Register to enable
Autonomous Performance Level Selection. Platforms that exclusively support Autonomous
Selection must populate this field as an Integer with a value of 1.
When Autonomous Selection is enabled, the platform is responsible for selecting performance
states. OSPM is not required to assess processor workload performance demand and convey a
corresponding performance delivery request to the platform via the Desired Performance Register.
8.4.7.1.6 Autonomous Activity Window Register
Optional
Register Location: System I/O, PCC, or Functional Fixed Hardware
Attribute:
Read/Write
Size:
10 bit(s)
Units:
Bits 06:00 - Significand, Bits 09:07 - Exponent, Base_Time_Unit = 1E-6 seconds
(1 microsecond)
If supported by the platform, OSPM may write a time value (10^3-bit exp * 7-bit mantissa in 1µsec
units: 1us to 1270 sec) to this field to indicate a moving utilization sensitivity window to the
platform's autonomous selection policy. Combined with the Energy Performance Preference
Register value, the Activity Window influences the rate of performance increase / decrease of the
platform's autonomous selection policy. OSPM writes a zero value to this register to enable the
platform to determine an appropriate Activity Window depending on the workload.
Writes to this register only have meaning when Autonomous Selection is enabled.
8.4.7.1.7 Energy Performance Preference Register
Optional
Register Location: System I/O, PCC, or Functional Fixed Hardware
Attribute:
Read/Write
Size:
4-8 bit(s
If supported by the platform, OSPM may write a range of values from 0 (performance preference) to
0xFF (energy efficiency preference) that influences the rate of performance increase /decrease and
the result of the hardware's energy efficiency and performance optimization policies.This provides a
means for OSPM to limit the energy efficiency impact of the platform's performance-related
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