ia-32_instruction-set-ref_a-m

D is not generated this condition is simply signaled

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Unformatted text preview: Architecture Compatibility section below. Description Stores the current value of the FPU control word at the specified destination in memory. The FSTCW instruction checks for and handles pending unmasked floatingpoint exceptions before storing the control word; the FNSTCW instruction does not. The assembler issues two instructions for the FSTCW instruction (an FWAIT instruction followed by an FNSTCW instruction), and the processor executes each of these instructions in separately. If an exception is generated for either of these instructions, the save EIP points to the instruction that caused the exception. This instruction's operation is the same in non-64-bit modes and 64-bit mode. IA-32 Architecture Compatibility When operating a Pentium or Intel486 processor in MS-DOS compatibility mode, it is possible (under unusual circumstances) for an FNSTCW instruction to be interrupted prior to being executed to handle a pending FPU exception. See the section titled "No-Wait FPU Instructions Can Get FPU Interrupt in Window" in Appendix D of the Intel 64 and IA-32 Architectures Software Developer's Manual, Volume 1, for a description of these circumstances. An FNSTCW instruction cannot be interrupted in this way on a Pentium 4, Intel Xeon, or P6 family processor. Operation DEST FPUControlWord; FPU Flags Affected The C0, C1, C2, and C3 flags are undefined. Floating-Point Exceptions None. Vol. 2 3-387 INSTRUCTION SET REFERENCE, A-M Protected Mode Exceptions #GP(0) If the destination is located in a non-writable segment. If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If the DS, ES, FS, or GS register is used to access memory and it contains a NULL segment selector. #SS(0) #NM #PF(fault-code) #AC(0) If a memory operand effective address is outside the SS segment limit. CR0.EM[bit 2] or CR0.TS[bit 3] = 1. If a page fault occurs. If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3. Real-Address Mode Exceptions #GP #SS #NM If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If a memory operand effective address is outside the SS segment limit. CR0.EM[bit 2] or CR0.TS[bit 3] = 1. Virtual-8086 Mode Exceptions #GP(0) #SS(0) #NM #PF(fault-code) #AC(0) If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If a memory operand effective address is outside the SS segment limit. CR0.EM[bit 2] or CR0.TS[bit 3] = 1. If a page fault occurs. If alignment checking is enabled and an unaligned memory reference is made. Compatibility Mode Exceptions Same exceptions as in Protected Mode. 3-388 Vol. 2 INSTRUCTION SET REFERENCE, A-M 64-Bit Mode Exceptions #SS(0) #GP(0) #NM #MF #PF(fault-code) #AC(0) If a memory address referencing the SS segment is in a noncanonical form. If the memory address is in a non-canonical form. CR0.EM[bit 2] or CR0.TS[bit 3] = 1. If there is a pending x87 FPU exception. If a pa...
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This note was uploaded on 10/01/2013 for the course CPE 103 taught by Professor Watlins during the Winter '11 term at Mississippi State.

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