Cke Power-Down; Self Refresh - Intel Xeon Processor E5-1600 Datasheet

• CKE Power-Down: Opportunistic, per rank control after idle time. There may be
different levels.
— Active Power-Down.
— Precharge Power-Down with Fast Exit.
— Precharge power Down with Slow Exit.
• Self Refresh: In this mode no transaction is executed. The DDR consumes the
minimum possible power.
4.3.1

CKE Power-Down

The CKE input land is used to enter and exit different power-down modes. The memory
controller has a configurable activity timeout for each rank. Whenever no reads are
present to a given rank for the configured interval, the memory controller will transition
the rank to power-down mode.
The memory controller transitions the DRAM to power-down by de-asserting CKE and
driving a NOP command. The memory controller will tri-state all DDR interface lands
except CKE (de-asserted) and ODT while in power-down. The memory controller will
transition the DRAM out of power-down state by synchronously asserting CKE and
driving a NOP command.
When CKE is off the internal DDR clock is disabled and the DDR power is significantly
reduced.
The DDR defines three levels of power-down:
• Active power-down.
• Precharge power-down fast exit.
• Precharge power-down slow exit.
4.3.2

Self Refresh

The Power Control Unit (PCU) may request the memory controller to place the DRAMs
in self refresh state. Self refresh per channel is supported. The BIOS can put the
channel in self-refresh if software remaps memory to use a subset of all channels. Also
processor channels can enter self refresh autonomously without PCU instruction when
the package is in a package C0 state.
4.3.2.1 Self Refresh Entry
Self refresh entrance can be either disabled or triggered by an idle counter. The idle
counter always clears with any access to the memory controller and remains clear as
long as the memory controller is not drained. As soon as the memory controller is
drained, the counter starts counting, and when it reaches the idle-count, the memory
controller will place the DRAMs in self refresh state.
Power may be removed from the memory controller core at this point. But V
(1.5 V or 1.35 V) to the DDR IO must be maintained.
4.3.2.2 Self Refresh Exit
Self refresh exit can be either a message from an external unit or as reaction for an
incoming transaction.
98 Intel® Xeon® Processor E5-1600/E5-2600/E5-4600 Product Families
Power Management
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Datasheet Volume One