Intel X3330 - Xeon 2.66 Ghz 6M L2 Cache 1333MHz FSB LGA775 Quad-Core Processor Specification page 19

buffer. The information in the PEBS record represents the state of the next instruction
to be executed following the counter overflow. Due to this erratum, if the counter
overflow occurs after execution of either MOV SS or STI, storage of the PEBS record is
delayed by one instruction.
Implication: When this erratum occurs, software may observe storage of the PEBS record being
delayed by one instruction following execution of MOV SS or STI. The state information
in the PEBS record will also reflect the one instruction delay.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
AAA8. Performance Monitoring Event FP_MMX_TRANS_TO_MMX May Not
Count Some Transitions
Problem: Performance Monitor Event FP_MMX_TRANS_TO_MMX (Event CCH, Umask 01H) counts
transitions from x87 Floating Point (FP) to MMX™ instructions. Due to this erratum, if
only a small number of MMX instructions (including EMMS) are executed immediately
after the last FP instruction, a FP to MMX transition may not be counted.
Implication: The count value for Performance Monitoring Event FP_MMX_TRANS_TO_MMX may be
lower than expected. The degree of undercounting is dependent on the occurrences of
the erratum condition while the counter is active. Intel has not observed this erratum
with any commercially available software.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
AAA9. A REP STOS/MOVS to a MONITOR/MWAIT Address Range May Prevent
Triggering of the Monitoring Hardware
Problem: The MONITOR instruction is used to arm the address monitoring hardware for the
subsequent MWAIT instruction. The hardware is triggered on subsequent memory
store operations to the monitored address range. Due to this erratum, REP STOS/
MOVS fast string operations to the monitored address range may prevent the actual
triggering store to be propagated to the monitoring hardware.
Implication: A logical processor executing an MWAIT instruction may not immediately continue
program execution if a REP STOS/MOVS targets the monitored address range.
Workaround: Software can avoid this erratum by not using REP STOS/MOVS store operations within
the monitored address range.
Status: For the steppings affected, see the Summary Tables of Changes.
AAA10. Performance Monitoring Event MISALIGN_MEM_REF May Over Count
Problem: Performance monitoring event MISALIGN_MEM_REF (05H) is used to count the number
of memory accesses that cross an 8-byte boundary and are blocked until retirement.
Due to this erratum, the performance monitoring event MISALIGN_MEM_REF also
counts other memory accesses.
Implication: The performance monitoring event MISALIGN_MEM_REF may over count. The extent of
the over counting depends on the number of memory accesses retiring while the
counter is active.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
Intel® Xeon® Processor 3300 Series
Specification Update January 2012
19