Hi all, I am trying to figure out the procedure that Linux follows for shutting down an x86 based system when ACPI is not used. From what I've found, when we try to shutdown the system from user-space, _reboot() system call is called with "LINUX_REBOOT_CMD_POWER_OFF" as argument. By tracking down the steps performed in the kernel when the aforementioned system call is involved, I ended up in kernel_power_off(), unlock_kernel(), and finaly do_exit() functions. The kernel_power_off() ultimately calls the native_machine_shutdown() form which Linux disables LAPIC, I/O APIC, HPET, etc. Then, after calling the unlock_kernel(), the do_exit() is called for ultimately shutting down the system. In the end of this function, I can see that the processor enters an infinite loop from which it repeatedly executes NOP instructions. That is actually the behaviour that I experience when I am not using ACPI; the system is not actually turning off but it goes into an idle state. Is this how Linux should act when ACPI is not used? I would expect in this case Linux to invoke an SMI so that the appropriate SMI function actually shutdown the system but I can't see where (and if) that takes place. Any help will be greatly appreciated. John K.