Specifications

Product Errata 77
Revision Guide for AMD Athlon™ 64 and AMD Opteron™ Processors
25759 Rev. 3.79 July 2009
117 Incorrect Value May Be Returned When Reading ChipKill ECC
Syndrome
Description
The 16 bits of the ChipKill ECC syndrome are logged in the MC4_STATUS register.
During a small window while the processor is updating the syndrome bits for a correctable or
uncorrectable error, a read of the MC4_STATUS register may return an incorrect syndrome value.
This erratum does not occur if the MC4_STATUS register already contains information on an
uncorrectable error.
Potential Effect on System
ECC logging software may not be able to uniquely identify the DIMM with the error. However, the
failing address that is logged allows the error to be isolated to a pair of DIMMs.
Suggested Workaround
Machine check logging software can read the MC4_STATUS register multiple times until a consistent
value is obtained. Since the failing window is short and occurs only when encountering a Chipkill
ECC error during the read, a consistent value is immediately obtained in nearly all cases.
Fix Planned
Yes