Datasheet

Intel® S5000 Server Board Family Datasheet System BIOS

Revision 1.3

Intel order number D38960-006

on the feature in BIOS Setup. With sparing enabled, the total effective memory size will be

reduced by the size of the spare FBDIMM(s).

3.3.9.2.1 Dual-ranked DIMM Sparing

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. However, populating differently-ranked FBDIMMs for sparing is not a good

practice and may yield unpredictable results.

3.3.9.3 Minimum FBDIMM Population for Sparing

For FBDIMM sparing, the minimum population is at least two FBDIMMs on the same channel on

any branch. Selecting sparing from BIOS Setup will cause the BIOS to attempt enabling the

feature on both branches to begin with, but actual configuration for a given branch will depend

upon the population of FBDIMMs on that branch.

For example: Correct configurations for Branch 0 are DIMM A1, DIMM A2. An incorrect

configuration for Branch 0 is DIMM A1. Because there is only one FBDIMM, none is available to

act as a spare.

The spare FBDIMMs do not contribute to available physical memory under normal system

operation. The Effective Memory field on the BIOS Setup utility screen will indicate this absence

of memory for the sparing operation.

3.3.9.4 Memory Mirroring

Unlike memory sparing, the mirrored configuration is a redundant image of the memory, and

can continue to operate with some uncorrectable errors occur.

Memory mirroring is a RAS feature in which two identical images of memory data are

maintained, providing maximum redundancy. On the Intel

5000 MCH-based Intel server

boards, mirroring is achieved across Branch 0 and Branch 1 such that one of these branches is

the primary image and the other the secondary image. The memory controller always directs

read transactions to the primary branch. Write transactions are directed to both branches under

normal circumstances.

Because the available system memory is divided into a primary image and a copy of the image,

the effective system memory is reduced by one-half. For example, if the system is operating in

memory mirroring mode and the total size of the FBDIMMs is 1 GB, then the effective size of the

memory is 512 MB because half of the FBDIMMs are the secondary images.

For memory mirroring to work, participant FBDIMMs on the same DIMM sockets on the adjacent

branches must be identical in terms of technology, number of ranks, timing, and size.

The BIOS provides a setup option to enable memory mirroring. When memory mirroring is

enabled, the BIOS attempts to configure the memory system accordingly. If the FBDIMM

population is not suitable for mirroring, the BIOS disables mirroring and reverts to the default

non-RAS mode with maximum interleave, or to the single channel mode. The BIOS setup then

defaults to the eventual setting on the next boot.