FNOP

No Operation

Opcodes

Hex Mnemonic Encoding Long Mode Legacy Mode Description
D9 D0 FNOP None Valid Valid 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.

This instruction's operation is the same in non-64-bit modes and 64-bit mode.

Pseudo Code

(* No operation *)

FPU Flags Affected

C0, C1, C2, C3 undefined.

Exceptions

Floating-Point Exceptions

None.

64-Bit Mode Exceptions

Same exceptions as in protected mode.

Compatibility Mode Exceptions

Same exceptions as in protected mode.

Virtual-8086 Mode Exceptions

Same exceptions as in protected mode.

Real-Address Mode Exceptions

Same exceptions as in protected mode.

Protected Mode Exceptions

Exception Description
#UD If the LOCK prefix is used.
#MF If there is a pending x87 FPU exception.
#NM CR0.EM[bit 2] or CR0.TS[bit 3] = 1.