Specifications

64 Product Errata
25759 Rev. 3.79 July 2009
Revision Guide for AMD Athlon™ 64 and AMD Opteron™ Processors
104 DRAM Data Masking Feature Causes ChipKill ECC Failures
When Enabled With x8/x16 DRAM Devices
Description
ChipKill ECC uses 16 ECC bits to correct and detect symbol errors within 128 data bits. If the data
masking feature is enabled, the ECC bits are incorrectly calculated for partial writes to memory. This
causes incorrect ECC to be written to DRAM. This erratum applies to x8 or greater DRAM devices,
but not to x4 devices.
Potential Effect on System
Data corruption may result from this erratum.
Suggested Workaround
BIOS should disable the data masking feature when enabling ChipKill ECC with x8, x16 (or greater)
ECC DIMMs, by setting the DisDatMsk bit (Northbridge Configuration Register - MSR C001_001F,
bit 36).
Fix Planned
Yes