BIOS Initialization Intel® Server System S7000FC4UR
Revision 1.0
126
14.2.13 Memory Reliability, Availability, Serviceability (RAS)
14.2.13.1 RAS Features
The following memory RAS features are supported:
Memory scrub engine
Memory sparing
Memory mirroring
Automatic thermal throttling
14.2.13.2 Memory Scrub Engine
The chipset MCH incorporates a memory scrub engine. This integrated component, when
enabled, performs periodic checks on the memory cells. The scrub engine can identify and
correct Memory ECC Single-Bit Errors (SBE). The scrub engine can also identify ECC Multi-Bit
Errors (MBE). However, these errors are uncorrectable.
14.2.13.2.1 Types of Scrubbing Operations
Two types of scrubbing operations are possible:
Demand scrubbing – executes when an error is encountered during a normal read/write
of data.
Patrol scrubbing – proactively walks through populated memory space seeking soft
errors.
The BIOS enables both demand scrubbing and patrol scrubbing by default.
Demand scrubbing is not possible when memory mirroring is enabled. Therefore, the BIOS
disables it automatically if the memory is configured for mirroring.
14.2.13.3 Memory Sparing
The chipset MCH provides memory sparing capabilities. Sparing is a RAS feature. It involves
placing a FBDIMM rank in reserve. This allows it to be used to replace a failing FBDIMM rank at
runtime without bringing the system down.
Sparing is only supported in dual-channel mode and is configured on each branch
independently. The BIOS assigns one FBDIMM rank per branch to act as a spare (reserve)
rank.
14.2.13.3.1 Spared Memory Configurations
Spared memory configurations do not provide redundant copies of memory , In addition, the
system cannot continue to operate when an ECC Uncorrectable Error / Multi-Bit Error (UE/MBE)
occurs. The purpose of memory sparing is to provide runtime failure prediction for FBDIMM
ranks exceeding a specified frequency of ECC Correctable Error events in a given time period.
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