Method 6: return to 16-bit mode, call interrupt 0x19 (not if you're on efi).<p>Method 7: return to 16-bit mode, set cs to 0xf000 and jump to 0xfff0.<p>Linux used to use method 6, but it wasn't reliable either. Something tells me returning to 16-bit mode might not be possible for some hardware / driver combinations.
I don't know if anyone else remembers, but I think it was either Windows 95 or Windows 98 which, after selecting shut down, the eventual result would be a message that said, "It is now safe to turn off your computer." I remember thinking it was magic when the computer would actually turn itself off at this point.<p>This article provides a good explanation for why that behavior was necessary.
Wow - that's very interesting. So, what do most operating systems (aside from Apple presumably) normally do to get a consistent reboot?<p>Are they probing the hardware at install time? Do they just have a "table of things to try" the first time you reboot and then use the "successful thing" from then on?
I'm surprised the triple fault method doesn't reliably work - I thought that processors were guaranteed to restart if you do this; I suppose it doesn't guarantee that other components get reset in the same way.