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FSTENV            Store Environment              Exception Flags: None

FSTENV memory location

       Logic:      [memory location] . environment

     FSTENV stores the environment starting at memory location. For the
     8087, 80287, and 80387 in 16-bit format, the following information is
     written to memory:

                                Bits ------.
                           15                   0   Bytes
                          +---------------------+
                          |      Control Word   |0   |
                          |---------------------|    |
                          |      Status Word    |4   |
                          |---------------------|    |
                          |      Tag Word       |8   V
                          |---------------------|
                          | Instruction Pointer |12
                          |---------------------|
                          | IP bits 16-19       |16
                          |---------------------|
                          | Operand pointer     |20
                          |---------------------|
                          | OP bits 16-19       |24
                          +---------------------+
                              16 Bit Format

     For the 80387 in 32-bit format:

                         Bits ------.
     31                 16 15                   0   Bytes
     +------------------------------------------+
     |     Reserved       |      Control Word   |0   |
     |--------------------+---------------------|    |
     |     Reserved       |      Status Word    |4   |
     |--------------------+---------------------|    |
     |     Reserved       |      Tag Word       |8   V
     |------------------------------------------|
     |              Error Offset (EIP)          |12
     |------------------------------------------|
     |     Reserved       |      CS             |16
     |------------------------------------------|
     |              Data Operand Offset         |20
     |------------------------------------------|
     |     Reserved       |      DS             |24
     +------------------------------------------+
                       32 Bit Format

  --------------------------------------------------------------------------
   Operands            Clocks         Bytes           Example
   FSTENV mem_pointer  40-50+EA        4              FSTENV ENV_AREA
  --------------------------------------------------------------------------

        Note:          The no-wait form of this instruction is FNSTENV.