Specifications

142 Product Errata

41322 Rev. 3.84 August 2011

Revision Guide for AMD Family 10h Processors

610 Processor with Message-Triggered C1E Enabled May Report a

False L3 LRU or Tag Machine Check

Description

During an exit from message-triggered C1E state (LDTSTOP# deassertion) that is less than 10

microseconds after the STOPGRANT message, the processor may report a false uncorrectable

machine check exception for either an L3 LRU or tag error. The false machine check is due to an L3

stutter scrub happening while the L3 clocks are disabled.

L3 stutter scrubs are enabled when Clock Power/Timing Control 0 Register[StutterScrubEn]

(F3xD4[15]) is 1b, and BIOS enables this only when message-triggered C1E is enabled. This erratum

is exposed only when the minimum time from STOPGRANT message to LDTSTOP# deassertion is

violated. However, erratum #669 documents an additional circumstance under which a similar

condition may be observed even when the minimum time from STOPGRANT message to

LDTSTOP# deassertion is not violated. The BIOS and Kernel Developer’s Guide (BKDG) for

AMD Family 10h Processors, order# 31116 documents a minimum time of 16 microseconds between

these events.

Potential Effect on System

Uncorrectable machine check exception (#MC) for an L3 LRU or tag error. The MC4_STATUS

overflow) and bits 43:42 (L3 subcache) of MC4_STATUS may or may not be set.

This machine check also causes a sync flood and reboot, unless these mechanisms have been

disabled.

Suggested Workaround

BIOS should set F3x1B8[5] = 1b whenever message-triggered C1E is enabled (Clock Power/Timing

Control 0 Register[MTC1eEn], F3xD4[13] = 1b) to remove the conditions under which the improper

scrub can occur. Implementation of this workaround does not alter the required minimum time from

STOPGRANT message to LDTSTOP# deassertion.

Fix Planned