Datasheet

Errata
Specification Update 51
AH24. REP MOVS/STOS Executing with Fast Strings Enabled and Crossing
Page Boundaries with Inconsistent Memory Types May Use an
Incorrect Data Size or Lead to Memory-Ordering Violations.
Problem: Under certain conditions as described in the Intel
®
64 and IA-32 Architectures
Software Developer‟s Manual, section Out-of-Order Stores For string operations in
Pentium 4, Intel Xeon, and P6 Family Processors, the processor performs REP MOVS or
REP STOS as fast strings. Due to this erratum fast string REP MOVS/REP STOS
instructions that cross page boundaries from WB/WC memory types to UC/WP/WT
memory types, may start using an incorrect data size or may observe memory
ordering violations.
Implication: Upon crossing the page boundary the following may occur, dependent on the new
page memory type:
1. UC the data size of each write will now always be 8 bytes, as opposed to the
original data size.
2. WP the data size of each write will now always be 8 bytes, as opposed to the
original data size and there may be a memory ordering violation.
3. WT there may be a memory ordering violation.
Workaround: Software should avoid crossing page boundaries from WB or WC memory type to UC,
WP or WT memory type within a single REP MOVS or REP STOS instruction that will
execute with fast strings enabled.
Status: For the steppings affected, see the Summary Tables of Changes.
AH25. 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.
Problem: The following Bus Transaction Performance Monitor events are supposed to count all
local transactions:
 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
under count 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.