TESTUI

TESTUI — Determine User Interrupt Flag

Opcode/ Instruction	Op/ En	64/32 bit Mode Support	CPUID Feature Flag	Description
F3 0F 01 ED TESTUI	ZO	V/I	UINTR	Copies the current value of UIF into EFLAGS.CF.

Instruction Operand Encoding

Op/En	Tuple	Operand 1	Operand 2	Operand 3	Operand 4
ZO	N/A	N/A	N/A	N/A	N/A

Operation

CF ← UIF;
ZF ← AF ← OF ← PF ← SF ← 0;

Flags Affected

The ZF, OF, AF, PF, SF flags are cleared and the CF flags to the value of the user interrupt flag.

Protected Mode Exceptions

#UD The TESTUI instruction is not recognized in protected mode.

Real-Address Mode Exceptions

#UD The TESTUI instruction is not recognized in real-address mode.

Virtual-8086 Mode Exceptions

#UD The TESTUI instruction is not recognized in virtual-8086 mode.

Compatibility Mode Exceptions

#UD The TESTUI instruction is not recognized in compatibility mode.

64-Bit Mode Exceptions

#UD If the LOCK prefix is used. If executed inside an enclave. If CR4.UINTR = 0. If CPUID.07H.00H:EDX.UINTR[5] = 0.

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Source: Intel® 64 and IA-32 Architectures Software Developer's Manual, Combined Volumes (Order Number 325462-091US, March 2026)
Generated: 7-6-2026