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Specification Update 37
HSD78. Certain Performance Monitoring Events May Over Count Software
Demand Loads
Problem: The following performance monitor events should count the number of software
demand loads. However due to this erratum, they may also include requests from the
Next Page Prefetcher and over count.
OFFCORE_REQUESTS_OUTSTANDING.DEMAND_DATA (Event 60H; Umask 01H)
OFFCORE_REQUESTS.DEMAND_DATA (Event B0H; Umask 01H)
CYCLE_ACTIVITY.L2_Pending (Event A3H; Umask 01H)
L2_HIT_MISS.LOAD (Event 24H; Umask 01H)
Implication: The listed performance monitoring events may reflect a count higher than the actual
number of events.
Workaround: None identified.
Status: For the steppings affected, see the Summary Table of Changes.
HSD79. Accessing Nonexistent Uncore Performance Monitoring MSRs May Not
Signal a #GP
Problem: An access to an uncore Performance Monitor MSR beyond the number reported in the
MSR_UNC_CBO_CONFIG MSR (396H) bits[3:0] should signal a #GP (general-
protection exception); due to this erratum, the processor may hang instead of signaling
#GP.
Implication: When software accesses nonexistent uncore performance monitoring MSRs, the logical
processor may hang instead of signaling a #GP.
Workaround: It is possible for the BIOS to contain a workaround for this erratum.
Status: For the steppings affected, see the Summary Table of Changes.
HSD80. Call Stack Profiling May Produce Extra Call Records
Problem: The performance monitoring Call Stack Profiling function should not generate call
records for “zero length calls” (call instructions targeting the location following the
instruction). However, due to this erratum, the processor will produce call records for
zero length calls.
Implication: The performance monitoring LBR call stack MSRs are incorrect in the presence of “zero
length calls” because calls and returns do not match.
Workaround: None identified.
Status: For the steppings affected, see the Summary Table of Changes.
HSD81. Warm Reset May Fail or Lead to Incorrect Power Regulation
Problem: Due to this erratum, after a warm reset, the processor may fail to boot properly or may
cause power to be regulated to an incorrect level.
Implication: The processor may not be able to control the VR (Voltage Regulator) to advertised
specifications, leading to in a system hang, a machine check, or improper power
regulation.
Workaround: It is possible for the BIOS to contain a workaround for this erratum
Status: For the steppings affected, see the Summary Table of Changes.