Vol 1

Power Management
40 Intel® Xeon® Product 2800/4800/8800 v2 Product Family
Datasheet Volume One, February 2014
• L3 shared cache retains context and becomes inaccessible in this state.
• Additional power savings actions, as allowed by the exit latency requirements,
include putting Intel QPI and PCIe* links in L1, the uncore is not available, further
voltage reduction can be taken.
In package C3, the ring will be off and as a result no accesses to the LLC are possible.
The content of the LLC is preserved.
3.2.5.5 Package C6 State
A processor enters the package C6 low power state when:
• At least one core is in the C6 state.
• The other cores are in a C6 or lower power state, and the processor has been
granted permission by the platform.
• L3 shared cache retains context and becomes inaccessible in this state.
• Additional power savings actions, as allowed by the exit latency requirements,
include putting Intel SMI Gen2, Intel QPI and PCIe* links in L1, the uncore is not
available, further voltage reduction can be taken.
In package C6 state, all cores have saved their architectural state and have had their
core voltages reduced to zero volts. The LLC retains context, but no accesses can be
made to the LLC in this state, the cores must break out to the internal state package C2
for snoops to occur.
3.2.6 Package C-State Power Specifications
See Chapter 6, “Electrical Specifications”.
3.3 System Memory Power Management
The DDR3 power states can be summarized as the following:
• Normal operation (highest power consumption).
• 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.
3.3.1 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.