x86 Instruction Set Reference

FNOP - No operation

Opcode Mnemonic Description
D9 D0 FNOP No operation is performed.
Description

Performs no FPU operation. This instruction takes up space in the instruction stream but does not affect the FPU or machine context, except the EIP register.
Floating-Point Exceptions
None.
Protected Mode Exceptions
#NMEM or TS in CR0 is set.
Real-Address Mode Exceptions
#NMEM or TS in CR0 is set.
Virtual-8086 Mode Exceptions
#NMEM or TS in CR0 is set.