Specification Update

Errata
24 Specification Update
AM21 The PECI Controller Resets to the Idle State
Problem: After reset, the Platform Environment Control Interface (PECI) client controller should
first identify a PECI bus idle condition and only then search for the first rising edge.
Due to this erratum, the processor PECI controller resets into the “Idle Detected” state
upon processor reset. If another PECI device on the platform is attempting to send a
message as the processor PECI controller comes out of reset, the processor PECI
controller will typically experience a Frame Check Sequence error and move to the idle
state. Rarely, the processor PECI controller may interpret that the message was
intended for it and try to reply. In this case a message may be corrupted but this
situation will be caught and handled by the PECI error handling protocol.
Implication: The processor PECI controller resets to an incorrect state but the error handling
capability of PECI will resolve the situation so that the processor will be able to
respond to an incoming message immediately after reset and will not disregard an
incoming message that arrives before an idle bus is formally detected.
Workaround: No workaround is necessary due to the PECI error handling protocol.
Status: For the steppings affected, see the Summary Tables of Changes.
AM22 Some Bus Performance Monitoring Events May Not Count Local Events under
Certain Conditions
Problem: Many Performance Monitoring Events require core-specificity, which specifies which
core’s events are to be counted (local core, other core or both cores). Due to this
erratum, some Bus Performance Monitoring events may not count when the core-
specificity is set to the local core.
The following Bus Performance Monitoring events will not count power management
related events for local core-specificity:
• BUS_TRANS_ IO (Event: 6CH) – Will not count I/O level reads resulting from
package-resolved C-state
• BUS_TRANS_ANY (Event: 70H) – Will not count Stop-Grants
Implication: The count values for the affected events may be lower than expected. The degree of
undercount depends on the occurrence of erratum conditions while the affected events
are active.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.