HLT

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Halt the processor

Intel AMD
+ +


Definition:

HLT

Causes the processor to stop executing instruction flow and wait for the following interrupts and signals to occur:

  • Unmasked hardware interrupt (INTR)
  • Non-maskable interrupt (NMI)
  • System management interrupt (SMI)
  • Debug exception
  • BINIT#, INIT# and RESET# signals


Operation in pseudo code:

hlt()
{
   if (cpl) // current privilege level != 0
     throw #GP;

   enter_state(HALT);
}


Opcodes (x86/x64):

F4 - HLT -


EFLAGS


:31

:30

:29

:28

:27

:26

:25

:24

:23

:22
ID
:21
VIP
:20
VIF
:19
AC
:18
VM
:17
RF
:16

:15
NT
:14
IOPL
:13:12
OF
:11
DF
:10
IF
:9
TF
:8
SF
:7
ZF
:6

:5
AF
:4

:3
PF
:2

:1
CF
:0
0000000000------0--------0-0-1-


Annotated WinDbg disassembly (x86/x64):

f4              hlt
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