| Opcode | Instruction | Op/En | 64-Bit Mode | Compat/Leg Mode | Description |
|---|---|---|---|---|---|
| F4 | HLT | NP | Valid | Valid | Halt |
| Op/En | Operand 1 | Operand 2 | Operand 3 | Operand 4 |
| NP | NA | NA | NA | NA |
Stops instruction execution and places the processor in a HALT state. An enabled interrupt (including NMI and SMI), a debug exception, the BINIT# signal, the INIT# signal, or the RESET# signal will resume execution. If an interrupt (including NMI) is used to resume execution after a HLT instruction, the saved instruction pointer (CS:EIP) points to the instruction following the HLT instruction.
When a HLT instruction is executed on an Intel 64 or IA-32 processor supporting Intel Hyper-Threading Technology, only the logical processor that executes the instruction is halted. The other logical processors in the physical processor remain active, unless they are each individually halted by executing a HLT instruction.
The HLT instruction is a privileged instruction. When the processor is running in protected or virtual-8086 mode, the privilege level of a program or procedure must be 0 to execute the HLT instruction.
This instruction’s operation is the same in non-64-bit modes and 64-bit mode.
Enter Halt state;
None.
| #GP(0) | If the current privilege level is not 0. |
| #UD | If the LOCK prefix is used. |
None.
Same exceptions as in protected mode.
Same exceptions as in protected mode.
Same exceptions as in protected mode.