Datasheet

Errata
44 Specification Update
AR62. 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.
AR63. 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: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
AR64. 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.
Status: For the steppings affected, see the Summary Tables of Changes.