Datasheet

Errata
58 Specification Update
AH41. PREFETCHh Instructions May Not Be Executed When Alignment Check
(AC) Is Enabled
Problem: PREFETCHT0, PREFETCHT1, PREFETCHT2 and PREFETCHNTA instructions may not be
executed when Alignment Check is enabled.
Implication: PREFETCHh instructions may not perform the data prefetch if Alignment Check is
enabled.
Workaround: Clear the AC flag (bit 18) in the EFLAGS register and/or the AM bit (bit 18) of Control
Register CR0 to disable alignment checking.
Status: For the steppings affected, see the Summary Tables of Changes.
AH42. Upper 32 Bits of the FPU Data (Operand) Pointer in the FXSAVE
Memory Image May Be Unexpectedly All 1's after FXSAVE
Problem: The upper 32 bits of the FPU Data (Operand) Pointer may incorrectly be set to all 1's
instead of the expected value of all 0's in the FXSAVE memory image if all of the
following conditions are true:
 The processor is in 64-bit mode.
 The last floating point operation was in compatibility mode
 Bit 31 of the FPU Data (Operand) Pointer is set.
 An FXSAVE instruction is executed
Implication: Software depending on the full FPU Data (Operand) Pointer may behave
unpredictably.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
AH43. Concurrent Multi-processor Writes to Non-dirty Page May Result in
Unpredictable Behavior
Problem: When a logical processor writes to a non-dirty page, and another logical-processor
either writes to the same non-dirty page or explicitly sets the dirty bit in the
corresponding page table entry, complex interaction with internal processor activity
may cause unpredictable system behavior.
Implication: This erratum may result in unpredictable system behavior and hang.
Workaround: It is possible for BIOS to contain a workaround for this erratum.
Status: For the steppings affected, see the Summary Tables of Changes.