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Dual-Core Intel Xeon Processor 5100 Series Specification Update
Implication: In this case, the phrase "unexpected or unpredictable execution behavior"
encompasses the generation of most of the exceptions listed in the Intel Architecture
Software Developer's Manual Volume 3: System Programming Guide, including a
General Protection Fault (GPF) or other unexpected behaviors. In the event that
unpredictable execution causes a GPF the application executing the unsynchronized
XMC operation would be terminated by the operating system.
Workaround: In order to avoid this erratum, programmers should use the XMC synchronization
algorithm as detailed in the Intel Architecture Software Developer's Manual Volume 3:
System Programming Guide, Section: Handling Self- and Cross-Modifying Code.
Status:
For the steppings affected, see the Summary Tables of Changes.
AG34.
MSRs Actual Frequency Clock Count (IA32_APERF) or Maximum
Frequency Clock Count (IA32_MPERF) May Contain Incorrect Data
after a Machine Check Exception (MCE)
Problem:
When an MCE occurs during execution of a RDMSR instruction for MSRs Actual
Frequency Clock Count (IA32_APERF) or Maximum Frequency Clock Count
(IA32_MPERF), the current and subsequent RDMSR instructions for these MSRs may
contain incorrect data.
Implication: After an MCE event, accesses to the IA32_APERF and IA32_MPERF MSRs may return
incorrect data. A subsequent reset will clear this condition.
Workaround: None identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
AG35.
Incorrect Address Computed For Last Byte of FXSAVE/FXRSTOR
Image Leads to Partial Memory Update
Problem:
A partial memory state save of the 512-byte FXSAVE image or a partial memory state
restore of the FXRSTOR image may occur if a memory address exceeds the 64KB limit
while the processor is operating in 16-bit mode or if a memory address exceeds the
4GB limit while the processor is operating in 32-bit mode.
Implication: FXSAVE/FXRSTOR will incur a #GP fault due to the memory limit violation as expected
but the memory state may be only partially saved or restored.
Workaround: Software should avoid memory accesses that wrap around the respective 16-bit and
32-bit mode memory limits.
Status:
For the steppings affected, see the Summary Tables of Changes.
AG36.
Split Locked Stores May not Trigger the Monitoring Hardware
Problem:
Logical processors normally resume program execution following the MWAIT, when
another logical processor performs a write access to a WB cacheable address within the
address range used to perform the MONITOR operation. Due to this erratum, a logical
processor may not resume execution until the next targeted interrupt event or O/S
timer tick following a locked store that spans across cache lines within the monitored
address range.
Implication: The logical processor that executed the MWAIT instruction may not resume execution
until the next targeted interrupt event or O/S timer tick in the case where the
monitored address is written by a locked store which is split across cache lines.
Workaround: Do not use locked stores that span cache lines in the monitored address range.
Status:
For the steppings affected, see the Summary Tables of Changes.
AG37.
REP CMPS/SCAS Operations May Terminate Early in 64-bit Mode when
RCX >= 0X100000000
Problem:
REP CMPS (Compare String) and SCAS (Scan String) instructions in 64-bit mode may
terminate before the count in RCX reaches zero if the initial value of RCX is greater
than or equal to 0X100000000.