Technical Product Specification

Table Of Contents
Functional Architecture Intel
®
Server Board S5400SF TPS
Revision 2.02
Intel order number: D92944-007
26
When the branch operates in the single-channel mode, the MCH supports an 8-byte-over-32-
byte Single Error Correct, Double Error Detect (SECDED+) code. It is the same ECC code that
is used in the dual-channel mode, but the number of devices over which the codeword is
defined is half, thereby reducing the SDDC properties to SECDED+. A single wire fault in the
same device is replicated across all symbols reducing the effectiveness of the error correction.
In the single DIMM mode (e.g. nine x8 devices), single wire fault (stuck at) errors or permanent
full device faults cannot be corrected. This code has the following properties:
Detection of any two bits in error within 8 bytes of data
Correction of any single bit in error within 8 bytes of data
Correction to any single DRAM data bus wire failure
3.2.3.6 Memory Sparing
The MCH provides DIMM sparing capabilities. DIMM Sparing is a RAS feature that places
DIMMs in reserve to replace DIMMs that are failing. Spared memory configurations do not
provide redundant copies of memory and the system cannot continue to operate when an
uncorrectable error occurs. The purpose of memory sparing is to detect a degrading FBDIMM
before it causes a system crash. Once the affected FBDIMM is isolated and removed from the
set of active FBDIMMs, the system integrity is maintained by copying the data from the failed
FBDIMM to the reserved FBDIMM. DIMM sparing occurs within a given channel of memory and
is not supported across branches.
The DIMM sparing feature requires that the spare FBDIMM be at least the size of the largest
primary FBDIMM in use. When sparing is enabled, the BIOS selects the spare automatically
during POST. No manual configuration of this feature is required beyond enabling the feature in
the BIOS setup. With sparing enabled, the total effective memory size is reduced by the size of
the spare FBDIMM(s).
For FBDIMM sparing, the minimum population is at least two FBDIMMs on the same channel on
any branch. Selecting the Memory RAS Sparing option from the BIOS setup causes the BIOS to
attempt enabling the feature on both branches to begin with, but actual configuration for a given
branch depends upon the population of FBDIMMs on that branch.
See Table 8 in section 1.1.1.1 for valid memory configurations that support the Memory Sparing
feature.
The spare FBDIMMs do not contribute to available physical memory under normal system
operation. The Effective Memory field on the BIOS Setup screen indicates this absence of
memory for the sparing operation.
When a dual-ranked FBDIMM is used as a spare, the BIOS has the ability to independently
select a physical rank on that FBDIMM as the spare unit and utilize the other physical rank as a
normal unit. This selective sparing ensures maximization of available memory while still
providing RAS.