Intel Xeon Processor LV and ULV Specification Update

Errata
18 Specification Update
Errata
AF1. FST Instruction with Numeric and Null Segment Exceptions May take
Numeric Exception with Incorrect FPU Operand Pointer
Problem: If execution of an FST (Store Floating Point Value) instruction would generate both
numeric and null segment exceptions, the numeric exception may be taken first and
with the Null x87 FPU Instruction Operand (Data) Pointer.
Implication: Due to this erratum, on an FST instruction the processor reports a numeric exception
instead of reporting an exception because of a Null segment. If the numeric exception
handler tries to access the FST data it will get a #GP fault. Intel has not observed this
erratum with any commercially available software, or system
Workaround: The numeric exception handler should check the segment and if it is Null avoid further
access to the data that caused the fault.
Status: For the steppings affected, see the Summary Tables of Changes.
AF2. Code Segment Limit Violation May Occur on 4 Gbyte Limit Check Title
Case
Problem: Code Segment limit violation may occur on 4 Gbyte limit check when the code stream
wraps around in a way that one instruction ends at the last byte of the segment and
the next instruction begins at 0x0.
Implication: This is a rare condition that may result in a system hang. Intel has not observed this
erratum with any commercially available software, or system
Workaround: Avoid code that wraps around segment limit.
Status: For the steppings affected, see the Summary Tables of Changes.
AF3. POPF and POPFD Instructions That Set the Trap Flag Bit May Cause
Unpredictable Processor Behavior
Problem: In some rare cases, POPF and POPFD instructions that set the Trap Flag (TF) bit in the
EFLAGS register (causing the processor to enter Single-Step mode) may cause
unpredictable processor behavior.
Implication: Single-Step operation is typically enabled during software debug activities, not during
normal system operation.
Workaround: There is no workaround for Single-Step operation in commercially available software.
For debug activities on custom software the POPF and POPFD instructions could be
immediately followed by a NOP instruction to facilitate correct execution.
Status: For the steppings affected, see the Error! Reference source not found..