Intel 2955U CL8064701523900 Data Sheet

The processor provides an auxiliary mechanism that allows system software to force

the processor to reduce its power consumption using clock modulation. This

mechanism is referred to as "On-Demand" mode and is distinct from Adaptive Thermal

Monitor and bi-directional PROCHOT#. The processor platforms must not rely on

software usage of this mechanism to limit the processor temperature. On-Demand

Mode can be accomplished using processor MSR or chipset I/O emulation. On-Demand

Mode may be used in conjunction with the Adaptive Thermal Monitor. However, if the

system software tries to enable On-Demand mode at the same time the TCC is

engaged, the factory configured duty cycle of the TCC will override the duty cycle

selected by the On-Demand mode. If the I/O based and MSR-based On-Demand

modes are in conflict, the duty cycle selected by the I/O emulation-based On-Demand

mode will take precedence over the MSR-based On-Demand Mode.

If Bit 4 of the IA32_CLOCK_MODULATION MSR is set to a 1, the processor will

immediately reduce its power consumption using modulation of the internal core clock,

independent of the processor temperature. The duty cycle of the clock modulation is

programmable using bits [3:1] of the same IA32_CLOCK_MODULATION MSR. In this

mode, the duty cycle can be programmed in either 12.5% or 6.25% increments

(discoverable using CPUID). Thermal throttling using this method will modulate each

processor core's clock independently.

I/O emulation-based clock modulation provides legacy support for operating system

software that initiates clock modulation through I/O writes to ACPI defined processor

clock control registers on the chipset (PROC_CNT). Thermal throttling using this

method will modulate all processor cores simultaneously.

The processor provides thermal protection for system memory by throttling memory

traffic when using either DIMM modules or a memory down implementation. Two

levels of throttling are supported by the processor – either a warm threshold or hot

threshold that is customizable through memory mapped I/O registers. Throttling

based on the warm threshold should be an intermediate level of throttling. Throttling

based on the hot threshold should be the most severe. The amount of throttling is

dynamically controlled by the processor.

Memory temperature can be acquired through an on-board thermal sensor (TS-on-

Board), retrieved by an embedded controller and reported to the processor through

the PECI 3.0 interface. This methodology is known as PECI injected temperatures and

is a method of Closed Loop Thermal Management (CLTM). CLTM requires the use of a

physical thermal sensor. EXTTS# is another method of CLTM; however, it is only

capable of reporting memory thermal status to the processor. EXTTS# consists of two

GPIO pins on the PCH where the state of the pins is communicated internally to the

processor.

Mobile 4th Generation Intel

®

 Core

™

 Processor Family, Mobile Intel

®

 Pentium

®

 Processor Family, and Mobile Intel

®

 Celeron

®

Processor Family

Datasheet – Volume 1 of 2

July 2014

70

Order No.: 329001-007