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BJ38.
FP Data Operand Pointer May Be Incorrectly Calculated After an FP
Access Which Wraps a 4-Gbyte Boundary in Code That Uses 32-Bit
Address Size in 64-bit Mode
Problem:
The FP (Floating Point) Data Operand Pointer is the effective address of the operand
associated with the last non-control FP instruction executed by the processor. If an 80-
bit FP access (load or store) uses a 32-bit address size in 64-bit mode and the memory
access wraps a 4-Gbyte boundary and the FP environment is subsequently saved, the
value contained in the FP Data Operand Pointer may be incorrect.
Implication:
Due to this erratum, the FP Data Operand Pointer may be incorrect. Wrapping an 80-bit
FP load around a 4-Gbyte boundary in this way is not a normal programming practice.
Intel has not observed this erratum with any commercially available software.
Workaround:
If the FP Data Operand Pointer is used in a 64-bit operating system which may run code
accessing 32-bit addresses, care must be taken to ensure that no 80-bit FP accesses
are wrapped around a 4-Gbyte boundary.
Status:
For the steppings affected, see the Summary Tables of Changes.
BJ39.
FP Data Operand Pointer May Be Incorrectly Calculated After an FP
Access Which Wraps a 64-Kbyte Boundary in 16-Bit Code
Problem:
The FP (Floating Point) Data Operand Pointer is the effective address of the operand
associated with the last non-control FP instruction executed by the processor. If an 80-
bit FP access (load or store) occurs in a 16-bit mode other than protected mode (in
which case the access will produce a segment limit violation), the memory access
wraps a 64-Kbyte boundary, and the FP environment is subsequently saved, the value
contained in the FP Data Operand Pointer may be incorrect.
Implication:
Due to this erratum, the FP Data Operand Pointer may be incorrect. Wrapping an 80-bit
FP load around a segment boundary in this way is not a normal programming practice.
Intel has not observed this erratum with any commercially available software.
Workaround:
If the FP Data Operand Pointer is used in an operating system which may run 16-bit FP
code, care must be taken to ensure that no 80-bit FP accesses are wrapped around a
64-Kbyte boundary.
Status:
For the steppings affected, see the Summary Tables of Changes.
BJ40.
Spurious Interrupts May be Generated From the Intel
Engine
Problem:
If software clears the F (Fault) bit 127 of the Fault Recording Register (FRCD_REG at
offset 0x208 in Remap Engine BAR) by writing 1b through RW1C command (Read Write
1 to Clear) when the F bit is already clear then a spurious interrupt from Intel
®
(Intel
Virtualization Technology for Directed I/O) Remap Engine may be observed.
Implication:
Due to this erratum, spurious interrupts will occur from the Intel VT-d Remap Engine
following RW1C clearing F bit.
Workaround:
None identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
32
®
VT-d Remap
®
VT-d
Specification Update
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