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Note: Package C6 state is the deepest C-state supported on discrete graphics systems with
PCI Express Graphics (PEG).
Package C7 state is the deepest C-state supported on integrated graphics systems (or
switchable graphics systems during integrated graphics mode). However, in most
configurations, package C6 will be more energy efficient than package C7 state. As a
result, package C7 state residency is expected to be very low or zero in most
scenarios where the display is enabled. Logic internal to the processor will determine
whether package C6 or package C7 state is the most efficient. There is no need to
make changes in BIOS or system software to prioritize package C6 state over package
C7 state.
4.3 Integrated Memory Controller (IMC) Power Management
The main memory is power managed during normal operation and in low-power ACPI
Cx states.
4.3.1
Disabling Unused System Memory Outputs
Any system memory (SM) interface signal that goes to a memory module connector in
which it is not connected to any actual memory devices is tri-stated. The benefits of
disabling unused SM signals are:
• Reduced power consumption.
• Reduced possible overshoot/undershoot signal quality issues seen by the
processor I/O buffer receivers caused by reflections from potentially un-
terminated transmission lines.
When a given rank is not populated, the corresponding chip select and CKE signals are
not driven.
At reset, all rows must be assumed to be populated, until it can be proven that they
are not populated.
CKE tristate should be enabled by BIOS where appropriate, since at reset all rows
must be assumed to be populated.
4.3.2
DRAM Power Management and Initialization
The processor implements extensive support for power management on the SDRAM
interface. There are four SDRAM operations associated with the Clock Enable (CKE)
signals, which the SDRAM controller supports. The processor drives four CKE pins to
perform these operations.
The CKE is one of the power-save means. When CKE is off, the internal DDR clock is
disabled and the DDR power is reduced. The power-saving differs according to the
selected mode and the DDR type used. For more information, refer to the IDD table in
the DDR specification.
The processor supports three different types of power-down modes in package C0.
The different power-down modes can be enabled through configuring
"PM_PDWN_config_0_0_0_MCHBAR". The type of CKE power-down can be configured
through PDWN_mode (bits 15:12) and the idle timer can be configured through
PDWN_idle_counter (bits 11:0). The different power-down modes supported are:
1. No power-down (CKE disable)
Processor—Power Management
Intel
®
Xeon
®
Processor E3-1200 v3 Product Family
Datasheet – Volume 1 of 2 June 2013
58 Order No.: 328907-001