Intel E7-8891 v2 CM8063601377422 User Manual

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PCU Functional Description
Processor E7-2800/4800/8800 v2 Product Family
Datasheet Volume Two: Functional Description, February 2014
many operating conditions under which one or more cores in the processor would be 
capable of running at much higher frequency without exceeding the power related 
constraints for the part. Furthermore, there are cases that the processor could exceed 
its rated power without exceeding the cooling capability of the platform, for significant 
duration or infinitely. 
DDR3 Power and Thermal Management
DRAM Power Management
The memory power meter uses Voltage Regulator (VR) current readings and/or 
activity counters to provide a running estimate of DRAM subsystem power. 
DRAM Thermal Throttling
The iMC module should estimate or sense the temperature of the DDR3 chips for two 
purposes. First is to tune the refresh rate to the temperature. Second reason is for 
thermal throttling. The system should use the best possible mean to sense the 
Miscellaneous Functions
PCU performs many functions which are not directly related to power and thermal 
management. Some of examples are:
• Socket Reset Flow: A significant portion of the socket reset flow is controlled 
by PCU
• Always ON APIC Timer: This function provides better support for Tickless OS. When 
cores are sleeping, PCU still keeps track of their APIC timers values and wakes the 
core up when necessary
• DRAM Throttling: PCU participates in DRAM thermal throttling solution. By taking 
advantage of PCU microcode, it is feasible to better model the temperature of 
DRAMs and reduce guardbands in open loop thermal throttling
• Manageability Support: PCU is the master of PECI interface which also carries 
processor manageability functions. PCU supports manageability functions which 
allow external BMC to read status information periodically (MSRs, CSRs, Error 
register, and so forth)
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