Server Board Family Datasheet

Intel® S5000 Server Board Family Datasheet System BIOS

Revision 1.3

Intel order number D38960-006

 Rule 5: The FBDIMM population of Slot 1 on Branch 0 determines the mode that is

selected. If DIMM_A1 and DIMM_B1 cannot lock-step, then the system reverts to single-

channel mode, with DIMM_B1 disabled.

 Rule 6: As long as Branch 1 cannot satisfy Rules 1 or 2, the Single-channel mode is

always given preference over dual-channel mode if the configuration on Slot 1, Branch 0

is not in balance (if DIMM_A1 and DIMM_B1 are not identical.)

 Rule 7: DIMM_A1 must always be populated, except the special case mentioned in

Rule 2. In addition, the BIOS will always select the mode of operation that best matches

the requirements of DIMM_A1, such that it is always enabled and used for runtime

memory. For example, in a FBDIMM population that has Branch 0 with only DIMM_A1

populated, the BIOS will forcibly initialize and configure single-channel mode with only

DIMM_A1 enabled, regardless of the number of FBDIMMs populated on Branch 1. Such

a method of upgrading system memory is, therefore, incorrect, and results in a reduced-

capacity operation. It must, therefore, be avoided.

 Rule 8: DIMM_A1 is the minimum possible FBDIMM configuration. In this configuration,

the memory operates in single-channel mode, and no RAS features are possible.

 Rule 9: The minimum memory population recommended by Intel for enabling Branch 1

is four FBDIMMs: DIMM_A1, DIMM_B1, DIMM_C1 and DIMM_D1.

 Rule 10: For a branch to operate in lock-step (dual-channel mode), the FBDIMMs in

socket positions on adjacent channels of the branch must be identical in terms of timing,

technology, and size. Therefore, DIMM_A1 and DIMM_B1 must be identical for Branch 1

to work in dual-channel mode.

If the FBDIMMs on adjacent channels of a branch are not identical, the FBDIMM on the

higher channel is disabled.

 Rule 11: FBDIMMs on adjacent slots on the same channel do not need to be identical.

 Rule 12: The minimum memory upgrade for memory mirroring is four FBDIMMs:

DIMM_A1, DIMM_B1, DIMM_C1 and DIMM_D1. Memory mirroring inherently relies on

the dual-channel mode of operation.

 Rule 13: The minimum population for memory pair sparing is four FBDIMMs in dual

channel mode: DIMM_A1, DIMM_A2, DIMM_B1, and DIMM_B2.

 Rule 14: Once the FBDIMMs installed on the adjacent channels of a branch have lock-

stepped, the resultant FBDIMM pair is treated as a single “logical” device thereafter.

Therefore, if one of the DIMMs in this lock-stepped pair fails Memory BIST or Channel

IBIST during POST, the BIOS will disable both FBDIMMs of the logical combination.

Similarly, if one of these DIMMs has a runtime transient uncorrectable error, both DIMMs

will be simultaneously disabled.

During the memory discovery phase of POST, the BIOS will disable any FBDIMM that does not

conform to the rules.

For platforms that support only a single FBD branch, such as the Intel

Server Board

S5000VSA, the same rules are applicable, except for rules that pertain to Branch 1.

3.3.7.3 Examples of FBDIMM Population and Upgrade Rules

See the server or workstation Technical Product Specification that applies to your product for

detailed information on FBDIMM population and upgrade rules.