B-40
INSTRUCTION FORMATS AND ENCODINGS
FSTP Store Real and Pop
32-bit memory
11011 001 : mod 011 r/m
64-bit memory
11011 101 : mod 011 r/m
80-bit memory
11011 011 : mod 111 r/m
ST(i)
11011 101 : 11 011 ST(i)
FSTSW Store Status Word into AX
11011 111 : 1110 0000
FSTSW Store Status Word into Memory
11011 101 : mod 111 r/m
FSUB Subtract
ST(0)
<
ST(0) 32-bit memory
11011 000 : mod 100 r/m
ST(0)
<
ST(0) 64-bit memory
11011 100 : mod 100 r/m
ST(d)
<
ST(0) ST(i)
11011 d00 : 1110 R ST(i)
FSUBP Subtract and Pop
ST(0)
<
ST(0) ST(i)
11011 110 : 1110 1 ST(i)
FSUBR Reverse Subtract
ST(0)
<
32-bit memory ST(0)
11011 000 : mod 101 r/m
ST(0)
<
64-bit memory ST(0)
11011 100 : mod 101 r/m
ST(d)
<
ST(i) ST(0)
11011 d00 : 1110 R ST(i)
FSUBRP Reverse Subtract and Pop
ST(i)
<
ST(i) ST(0)
11011 110 : 1110 0 ST(i)
FTST Test
11011 001 : 1110 0100
FUCOM Unordered Compare Real
11011 101 : 1110 0 ST(i)
FUCOMP Unordered Compare Real and Pop11011 101 : 1110 1 ST(i)
FUCOMPP Unordered Compare Real and Pop
Twice
11011 010 : 1110 1001
FUCOMI Unordered Compare Real and Set
EFLAGS
11011 011 : 11 101 ST(i)
FUCOMIP Unordered Compare Real, Set
EFLAGS, and Pop
11011 111 : 11 101 ST(i)
FXAM Examine
11011 001 : 1110 0101
FXCH Exchange ST(0) and ST(i)
11011 001 : 1100 1 ST(i)
FXTRACT Extract Exponent and Significand11011 001 : 1111 0100
FYL2X ST(1)
?
log
2
(ST(0))
11011 001 : 1111 0001
FYL2XP1 ST(1)
?
log
2
(ST(0) + 1.0)
11011 001 : 1111 1001
FWAIT Wait until FPU Ready
1001 1011
Table B-23. Floating-Point Instruction Formats and Encodings
Instruction and Format
Encoding
