Errata
Intel
®
Core™2 Extreme Quad-Core Processor QX6000
Δ
Sequence and 45
Intel
®
Core™2 Quad Processor Q6000
Δ
Sequence
Specification Update
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.
AK69. 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.
AK70. 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.
AK71. PMI May Be Delayed to Next PEBS Event
Problem: After a PEBS (Precise Event-Based Sampling) event, the PEBS index is
compared with the PEBS threshold, and the index is incremented with every
event. If PEBS index is equal to the PEBS threshold, a PMI (Performance
Monitoring Interrupt) should be issued. Due to this erratum, the PMI may be
delayed by one PEBS event.
Implication: Debug Store Interrupt Service Routines may observe delay of PMI occurrence
by one PEBS event.
Workaround: None identified.
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