Re: software reset

Eric W. Biederman
2003-04-30T10:55:29Z

Jamie Lokier <jamie@shareable.org> writes:

> Andi Kleen wrote:
> > The most reliable way is to force a triple fault; load zero into
> > the IDT register and then trigger an exception. The linux kernel
> > does that in fact for reboot and so far I haven't seen any machine failing
> > to reset yet.
>
> There are some 486s which don't boot on triple fault, nor on asking
> the keyboard controller to pulse the reset line. Hence the 3rd option,
> "reboot=bios".

And as an interesting data point all a triple fault does on a modern
system is to put the cpu in a weird stopped state. Some hardware
usually the southbridge then detects this and if properly configured
will trigger the reset line.

I believe this may actually go back into history as far as the 486 but
I have not done the researched to see how far back this behavior goes.

Eric