Intel E7-8891 v2 CM8063601377422 User Manual

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Processor E7-2800/4800/8800 v2 Product Family
Datasheet Volume Two: Functional Description, February 2014
PCU Functional Description
PCU Functional Description
This chapter describes the PCU module features along with PECI interfaces in more 
Power and thermal management functions require the collection of inputs from a wide 
variety of sources on the platform. These sources could be dedicated sensors in the 
processor or a collection of microarchitectural events. The inputs from these sources 
can be used to calculate macro parameters such as temperature, power and energy 
The operating system also provides performance requirements in the form of P-state 
requests and idle information in the form of C-state requests. This information can be 
used to optimize the current operating point to consume the minimum amount of 
power required.
The platform also provides inputs which are generally invisible to the OS. The 
PROCHOT_N signal is one such example, it indicates an overheating condition in one of 
the platform agents. Similarly platform agents like Board Management Controller 
(BMC) and Intel
 Management Engine (Intel
 ME) can monitor and set limits through 
PECI or DMI2 interfaces. The large variety of agents, sensors and the complex 
calculations required to compute optimal parameters has made power management a 
very complex function. The complexity has reached a point, where it justifies its own 
dedicated processing agent.
The PCU consists of a dedicated microcontroller; RAM for firmware (PCU microcode), 
HW state machines, I/O registers for interfacing to the microcontroller and interfaces to 
the hardware units in the processor. 
below shows the high level 
organization of power and thermal management architecture. There are two masters to 
the power management architecture, the operating system and HW agents in the 
platform. HW agents can be Intel ME in the PCH, BMC, Hardware Monitor in workstation 
segment. HW agents may override the OS requests when in conflict. For example; if 
the OS requests a P-state which exceeds the power limit set by the Intel ME, IT will be 
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