Intel387
TM
SX MATH COPROCESSOR
3.1.6 PROCESSOR INSTRUCTIONS
(ADMINISTRATIVE)
FINIT Initialize Math CoProcessor
FLDCW Load Control Word
FSTCW Store Control Word
FLDCW Load Status Word
FSTSW Store Status Word
FSTSW AX Store Status Word to AX register
FCLEX Clear Exceptions
FSTENV Store Environment
FLDENV Load Environment
FSAVE Save State
FRSTOR Restore State
FINCSTP Increment Stack pointer
FDECSTP Decrement Stack pointer
FFREE Free Register
FNOP No Operation
FWAIT Report Math CoProcessor Error
3.2 Register Set
Figure 3-1 shows the Intel387 SX Math CoProcessor
register set. When a Math CoProcessor is present in
a system, programmers may use these registers in
addition to the registers normally available on the
CPU.
i386
TM
Microprocessor Registers i387
TM
Math CoProcessor Data Registers
GENERAL REGISTERS
31 16 15 0
EAX
AX
AH AL
EBX
BX
BH BL
ECX
CX
CH CL
EDX
DX
DH DL
ESI SI
EDI DI
EBP BP
ESP SP
SEGMENT REGISTERS
15 0
CS
SS
DS
ES
FS
GS
31 0
EIP
EFLAGS
Tag
Field
79 78 64 63 0 1 0
R0 Sign Exponent Significand
R1
R2
R3
R4
R5
R6
R7
15 0
Control Register
Status Register
Tag Word
47 0
Instruction Pointer (in CPU)
Data Pointer (in CPU)
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
Figure 3-1. Intel386
TM
CPU and Intel387
TM
Math CoProcessor Register Set
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