processors. HLT halts the processor until the RESET
line is activated or an interrupt
is received. It takes two cycles
on an 8088
, two on a 186
, two on a 286
, five on a 386
, four on a 486
, and four on a 586
When the processor isn't doing a lot of number crunching, it's often waiting for user input or an i/o request to complete. Halting the processor effectively puts it into a suspended mode, consuming less power and therefore giving off less heat. In use it often decreases heat by 10 degrees centigrade.
Modern operating systems like Linux
or Windows NT
execute the HLT instruction in an idle priority thread.Windows 98
was supposed to have this feature but it was pulled out last minute.