Advanced Error Correction Code (lockstep)Advanced Error Correction Code (ECC) mode extends SDDC from x4 DRAM based DIMMs to both x4 andx8 DRAMs. This protects against single DRAM chip failures during normal operation.The installation guidelines for memory modules are as follows:• Memory modules must be identical in size, speed, and technology.• DIMMs installed in memory sockets with white release levers must be identical and the same ruleapplies for sockets with black release levers. This ensures that identical DIMMs are installed inmatched pair —for example, A1 with A2, A3 with A4, A5 with A6, and so on.Memory optimized (independent channel) modeThis mode supports Single Device Data Correction (SDDC) only for memory modules that use x4 devicewidth. It does not impose any specific slot population requirements.Memory sparingNOTE: To use memory sparing, this feature must be enabled in System Setup.In this mode, one rank per channel is reserved as a spare. If persistent correctable errors are detected ona rank, the data from this rank is copied to the spare rank, and the failed rank is disabled.With memory sparing enabled, the system memory available to the operating system is reduced by onerank per channel. For example, in a dual-processor configuration with sixteen 4 GB single-rank memorymodules, the available system memory is: 3/4 (ranks/channel) × 16 (memory modules) × 4 GB = 48 GB,and not 16 (memory modules) × 4 GB = 64 GB.NOTE: Memory sparing does not offer protection against a multi-bit uncorrectable error.NOTE: Both Advanced ECC/Lockstep and Optimizer modes support memory sparing.Sample memory configurationsThe following tables show sample memory configurations for one and two processor configurations thatfollow the appropriate memory guidelines.NOTE: 1R and 2R in the following tables indicate single- and dual-rank DIMMs respectively.Table 38. Memory configurations—single processorSystemCapacity (inGB)DIMM Size(in GB) Number ofDIMMs DIMM Rank,Organization, andFrequencyDIMM Slot Population4 4 1 1R, x8, 2400 MT/s,1R, x8, 2133 MT/s,1R, x8, 1866 MT/sA18 4 2 1R, x8, 2400 MT/s,1R, x8, 2133 MT/s,1R, x8, 1866 MT/sA1, A289
