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Specification Update 25
HSD28. Modified Compliance Patterns for 2.5 GT/s and 5 GT/s Transfer Rates
Do Not Follow PCIe* Specification
Problem: The PCIe controller does not produce the PCIe specification defined sequence for the
Modified Compliance Pattern at 2.5 GT/s and 5 GT/s transfer rates. This erratum is not
seen at 8 GT/s transfer rates.
Implication: Normal PCIe operation is unaffected by this erratum.
Workaround: None identified.
Status: For the steppings affected, see the Summary Table of Changes.
HSD29. Performance Monitor Counters May Produce Incorrect Results
Problem: When operating with SMT enabled, a memory at-retirement performance monitoring
event (from the list below) may be dropped or may increment an enabled event on the
corresponding counter with the same number on the physical core’s other thread rather
than the thread experiencing the event. Processors with SMT disabled in BIOS are not
affected by this erratum.
The list of affected memory at-retirement events is as follows:
MEM_UOP_RETIRED.LOADS
MEM_UOP_RETIRED.STORES
MEM_UOP_RETIRED.LOCK
MEM_UOP_RETIRED.SPLIT
MEM_UOP_RETIRED.STLB_MISS
MEM_LOAD_UOPS_RETIRED.HIT_LFB
MEM_LOAD_UOPS_RETIRED.L1_HIT
MEM_LOAD_UOPS_RETIRED.L2_HIT
MEM_LOAD_UOPS_RETIRED.LLC_HIT
MEM_LOAD_UOPS_MISC_RETIRED.LLC_MISS
MEM_LOAD_UOPS_LLC_HIT_RETIRED.XSNP_HIT
MEM_LOAD_UOPS_LLC_HIT_RETIRED.XSNP_HITM
MEM_LOAD_UOPS_LLC_HIT_RETIRED.XSNP_MISS
MEM_LOAD_UOPS_LLC_HIT_RETIRED.XSNP_NONE
MEM_LOAD_UOPS_RETIRED.LLC_MISS
MEM_LOAD_UOPS_LLC_MISS_RETIRED.LOCAL_DRAM
MEM_LOAD_UOPS_LLC_MISS_RETIRED.REMOTE_DRAM
MEM_LOAD_UOPS_RETIRED.L2_MISS
Implication: Due to this erratum, certain performance monitoring event will produce unreliable
results during hyper-threaded operation.
Workaround: None identified.
Status: For the steppings affected, see the Summary Table of Changes.
HSD30. Performance Monitor UOPS_EXECUTED Event May Undercount
Problem: The performance monitor event UOPS_EXECUTED (Event B1H, any Unmask) should
count the number of UOPs executed each cycle. However due to this erratum, when
eight UOPs execute in one cycle, these UOPs will not be counted.
Implication: The performance monitor event UOPS_EXECUTED may reflect a count lower than the
actual number of events.
Workaround: None identified.
Status: For the steppings affected, see the Summary Table of Changes.