Intel S2600CO series User Manual page 39

Intel® Server Board S2600CO Family TPS
3.2.2.4.2 Lockstep Channel Mode
In Lockstep Channel Mode the cache-line is split across channels. This is done to support
Single Device Data Correction (SDDC) for DRAM devices with 8-bit wide data ports. Also, the
same address is used on both channels, such that an address error on any channel is
detectable by bad ECC. The IMC module always accumulates 32-bytes before forwarding data
so there is no latency benefit for disabling ECC.
Lockstep channels must be populated identically. That is, each DIMM in one channel must have
a corresponding DIMM of identical organization (number ranks, number banks, number rows,
and number columns). DIMMs may be of different speed grades, but the IMC module will be
configured to operate all DIMMs according to the slowest parameters present by the Memory
Reference Code (MRC).
Channel 0 and Channel 1 can be in lockstep. Channel 2 and Channel 3 can be in lockstep.
Performance in lockstep mode cannot be as high as with independent channels. The burst
length for DDR3 DIMMs is eight which is shared between two channels that are in lockstep
mode. Each channel of the pair provides 32 bytes to produce the 64-byte cache-line. DRAMs on
independent channels are configured to deliver a burst length of eight. The maximum read
bandwidth for a given rank is half of peak. There is another drawback in using lockstep mode,
that is, higher power consumption since the total activation power is about twice of the
independent channel operation if comparing to same type of DIMMs.
3.2.2.4.3 Mirror Mode
Memory mirroring mode is the mechanism by which a component of memory is mirrored. In
mirrored mode, when a write is performed to one copy, a write is generated to the target
location as well. This guarantees that the target is always updated with the latest data from the
main copy. The IMC module supports mirroring across the corresponding mirroring channel
within the processor socket but not across sockets. DIMM organization in each slot of one
channel must be identical to the DIMM in the corresponding slot of the other channel. This
allows a single decode for both channels. When mirroring mode is enabled, memory image in
Channel 0 is maintained the same as Channel 1 and Channel 2 is maintained the same as
Channel 3.
3.2.2.5 Memory RAS Support
The server board supports the following memory RAS modes:
Single Device Data Correction (SDDC)

Error Correction Code (ECC) Memory

Demand Scrubbing for ECC Memory

Patrol scrubbing for ECC Memory

Rank Sparing Mode

Mirrored Channel Mode

Lockstep Channel Mode

Regardless of RAS mode, the requirements for populating within a channel given in the section
3.2.2.2 must be met at all times. Note that support of RAS modes that require matching DIMM
population between channels (Mirrored and Lockstep) require that ECC DIMMs be populated.
Revision 1.4
Intel order number G42278-004
Functional Architecture Overview
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