Advanced Ecc Memory - Compaq BL10e - HP ProLiant - 512 MB RAM Overview

Advanced ECC memory

To improve memory protection beyond standard ECC, HP introduced Advanced ECC technology in
1996. HP and most other server manufacturers use this solution in industry-standard products.
Advanced ECC can correct a multi-bit error that occurs within one DRAM chip; thus, it can correct a
complete DRAM chip failure. In Advanced ECC with 4-bit (x4) memory devices, each chip contributes
four bits of data to the data word. The four bits from each chip are distributed across four ECC
devices (one bit per ECC device), so that an error in one chip could produce up to four separate
single-bit errors. Figure 9 shows how one ECC device receives four data bits from four DRAM chips.
Figure 9. Advanced ECC
Since each ECC device can correct single-bit errors, Advanced ECC can actually correct a multi-bit
error that occurs within one DRAM chip. As a result, Advanced ECC provides device failure
protection (Table 1).
Table 1. Comparison of ECC and Advanced ECC error protection
Error Condition
Single-bit
Double-bit
DRAM failure
Although Advanced ECC provides failure protection, it can reliably correct multi-bit errors only when
they occur within a single DRAM chip. Advanced ECC does not provide failover capability. As a
result, if there is a memory failure, the system must be shut down before the memory can be replaced.
The latest generation of HP ProLiant servers offers two levels of Advanced Memory Protection that
provide increased fault tolerance for applications requiring higher levels of availability.
ECC Outcome
Correct
Detect
Detect
Advanced ECC Outcome
Correct
Correct or detect
Correct
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