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Power Management
4.3.2.3
Dynamic Power-down Operation
Dynamic power-down of memory is employed during normal operation. Based on idle
conditions, a given memory rank may be powered down. The IMC implements
aggressive CKE control to dynamically put the DRAM devices in a power-down state.
The processor core controller can be configured to put the devices in active power-
down (CKE de-assertion with open pages) or precharge power-down (CKE de-assertion
with all pages closed). Precharge power-down provides greater power savings but has
a bigger performance impact, since all pages will first be closed before putting the
devices in power-down mode.
If dynamic power-down is enabled, all ranks are powered up before doing a refresh
cycle and all ranks are powered down at the end of refresh.
4.3.2.4
DRAM I/O Power Management
Unused signals should be disabled to save power and reduce electromagnetic
interference. This includes all signals associated with an unused memory channel.
Clocks can be controlled on a per SO-DIMM basis. Exceptions are made for per SO-
DIMM control signals such as CS#, CKE, and ODT for unpopulated SO-DIMM slots.
The I/O buffer for an unused signal should be tri-stated (output driver disabled), the
input receiver (differential sense-amp) should be disabled, and any DLL circuitry
related ONLY to unused signals should be disabled. The input path must be gated to
prevent spurious results due to noise on the unused signals (typically handled
automatically when input receiver is disabled).
4.4
PCI Express* Power Management
• Active power management support using L0s, and L1 states.
• All inputs and outputs disabled in L2/L3 Ready state.
Note:
PEG interface does not support Hot Plug.
Note:
Power impact may be observed when PEG link disable power management state is
used.
4.5
Direct Media Interface (DMI) Power Management
• Active power management support using L0s/L1 state.
Datasheet, Volume 1
55
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