Intel E6600 Specification Update - Page 47

Performance Monitoring Event FP_ASSIST May Not be Accurate

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Errata AI68. Performance Monitoring Event FP_ASSIST May Not be Accurate Problem: Performance monitoring event FP_ASSIST (11H) may be inaccurate as assist events will be counted twice per actual assist in the following specific cases: • FADD and FMUL instructions with a NaN(Not a Number) operand and a memory operand • FDIV instruction with zero operand value in memory In addition, an assist event may be counted when DAZ (Denormals-Are-Zeros) and FTZ (Flush-To-Zero) flags are turned on even though no actual assist occurs. Implication: The counter value for the performance monitoring event FP_ASSIST (11H) may be larger than expected. The size of the error is dependent on the number of occurrences of the above conditions while the event is active. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. AI69. CPL-Qualified BTS May Report Incorrect Branch-From Instruction Address Problem: CPL (Current Privilege Level)-qualified BTS (Branch Trace Store) may report incorrect branch-from instruction address under the following conditions: • Either BTS_OFF_OS[9] or BTS_OFF_USR[10] is selected in IA32_DEBUGCTLC MSR (1D9H) • Privilege-level transitions occur between CPL > 0 and CPL 0 or vice versa. Implication: Due to this erratum, the From address reported by BTS may be incorrect for the described conditions. Workaround: None identified. Status: For the steppings affected, see the Summary Tables of Changes. AI70. PEBS Does Not Always Differentiate Between CPL-Qualified Events Problem: Performance monitoring counter configured to sample PEBS (Precise Event Based Sampling) events at a certain privilege level may count samples at the wrong privilege level. Implication: Performance monitoring counter may be higher than expected for CPLqualified events. Do not use performance monitoring counters for precise event sampling when the precise event is dependent on the CPL value. Workaround: Do not use performance monitoring counters for precise event sampling when the precise event is dependent on the CPL value. Status: For the steppings affected, see the Summary Tables of Changes. Intel® Core™2 Extreme Processor X6800 and Intel® Core™2 Duo Desktop Processor E6000 and E4000 Sequence 47 Specification Update

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Errata
Intel
®
Core™2 Extreme Processor X6800 and
Intel
®
Core™2 Duo Desktop Processor E6000 and E4000 Sequence
47
Specification Update
AI68.
Performance Monitoring Event FP_ASSIST May Not be Accurate
Problem:
Performance monitoring event FP_ASSIST (11H) may be inaccurate as assist
events will be counted twice per actual assist in the following specific cases:
•
FADD and FMUL instructions with a NaN(Not a Number) operand and a memory
operand
•
FDIV instruction with zero operand value in memory
In addition, an assist event may be counted when DAZ (Denormals-Are-Zeros) and
FTZ (Flush-To-Zero) flags are turned on even though no actual assist occurs.
Implication:
The counter value for the performance monitoring event FP_ASSIST (11H)
may be larger than expected. The size of the error is dependent on the
number of occurrences of the above conditions while the event is active.
Workaround:
None identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
AI69.
CPL-Qualified BTS May Report Incorrect Branch-From Instruction
Address
Problem:
CPL (Current Privilege Level)-qualified BTS (Branch Trace Store) may report
incorrect branch-from instruction address under the following conditions:
•
Either BTS_OFF_OS[9] or BTS_OFF_USR[10] is selected in IA32_DEBUGCTLC MSR
(1D9H)
•
Privilege-level transitions occur between CPL > 0 and CPL 0 or vice versa.
Implication:
Due to this erratum, the From address reported by BTS may be incorrect for
the described conditions.
Workaround:
None identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
AI70.
PEBS Does Not Always Differentiate Between CPL-Qualified Events
Problem:
Performance monitoring counter configured to sample PEBS (Precise Event
Based Sampling) events at a certain privilege level may count samples at the
wrong privilege level.
Implication:
Performance monitoring counter may be higher than expected for CPL-
qualified events. Do not use performance monitoring counters for precise
event sampling when the precise event is dependent on the CPL value.
Workaround:
Do not use performance monitoring counters for precise event sampling when
the precise event is dependent on the CPL value.
Status:
For the steppings affected, see the Summary Tables of Changes.