Technical Product Specification

Intel® Server Board S1400FP TPS Functional Architecture
Revision 2.0 Intel order number G64246-003 23
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.
Independent Channel Mode is the only mode that supports non-ECC DIMMs in addition to ECC
DIMMs.
For RAS modes that require matching populations, the same slot positions across channels
must hold the same DIMM type with regards to size and organization. DIMM timings do not
have to match but timings will be set to support all DIMMs populated (that is, DIMMs with slower
timings will force faster DIMMs to the slower common timing modes).
3.2.2.4.1 Independent Channel Mode
In non-ECC and x4 SDDC configurations, each channel is running independently (nonlock-
step), that is, each cache-line from memory is provided by a channel. To deliver the 64-byte
cache-line of data, each channel is bursting eight 8-byte chunks. Back to back data transfer in
the same direction and within the same rank can be sent back-to-back without any dead-cycle.
The independent channel mode is the recommended method to deliver most efficient power and
bandwidth as long as the x8 SDDC is not required.
3.2.2.4.2 Rank Sparing Mode
In Rank Sparing Mode, one rank is a spare of the other ranks on the same channel. The spare
rank is held in reserve and is not available as system memory. The spare rank must have
identical or larger memory capacity than all the other ranks (sparing source ranks) on the same
channel. After sparing, the sparing source rank will be lost.
Rank Sparing Mode enhances the system’s RAS capability by “swapping out” failing ranks of
DIMMs. Rank Sparing is strictly channel and rank oriented. Each memory channel is a Sparing
Domain.
For Rank Sparing to be available as a RAS option, there must be 2 or more single rank or dual
rank DIMMs, or at least one quad rank DIMM installed on each memory channel.
Rank Sparing Mode is enabled or disabled in the Memory RAS and Performance Configuration
screen in the <F2> Bios Setup Utility
When Sparing Mode is operational, for each channel, the largest size memory rank is reserved
as a “spare” and is not used during normal operations. The impact on Effective Memory Size is
to subtract the sum of the reserved ranks from the total amount of installed memory.
Hardware registers count the number of Correctable ECC Errors for each rank of memory on
each channel during operations and compare the count against a Correctable Error Threshold.
When the correctable error count for a given rank hits the threshold value, that rank is deemed
to be “failing”, and it triggers a Sparing Fail Over (SFO) event for the channel in which that rank
resides. The data in the failing rank is copied to the Spare Rank for that channel, and the Spare
Rank replaces the failing rank in the IMC’s address translation registers.
An SFO Event is logged to the BMC SEL. The failing rank is then disabled, and any further
Correctable Errors on that now non-redundant channel will be disregarded.