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Specification Update
AAN40.
Infinite Stream of Interrupts May Occur if an ExtINT Delivery Mode
Interrupt is Received while All Cores in C6
Problem:
If all logical processors in a core are in C6, an ExtINT delivery mode interrupt is
pending in the xAPIC and interrupts are blocked with EFLAGS.IF=0, the interrupt will
be processed after C6 wakeup and after interrupts are re-enabled (EFLAGS.IF=1).
However, the pending interrupt event will not be cleared.
Implication:
Due to this erratum, an infinite stream of interrupts will occur on the core servicing the
external interrupt. Intel has not observed this erratum with any commercially available
software/system.
Workaround:
None identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
AAN41.
Two xAPIC Timer Event Interrupts May Unexpectedly Occur
Problem:
If an xAPIC timer event is enabled and while counting down the current count reaches
1 at the same time that the processor thread begins a transition to a low power C-
state, the xAPIC may generate two interrupts instead of the expected one when the
processor returns to C0.
Implication:
Due to this erratum, two interrupts may unexpectedly be generated by an xAPIC timer
event.
Workaround:
None identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
AAN42.
EOI Transaction May Not be Sent if Software Enters Core C6 During an
Interrupt Service Routine
Problem:
If core C6 is entered after the start of an interrupt service routine but before a write to
the APIC EOI (End of Interrupt) register, and the core is woken up by an event other
than a fixed interrupt source the core may drop the EOI transaction the next time APIC
EOI register is written and further interrupts from the same or lower priority level will
be blocked.
Implication:
EOI transactions and interrupts may be blocked when core C6 is used during interrupt
service routines. Intel has not observed this erratum with any commercially available
software.
Workaround:
None identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
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