Max, SMIs happen for hundreds of reasons, many which have nothing to do
with power management. Even machines with power management turned off
in the BIOS trigger them all the time, usually for chipset bug fixups.
Basically, they are used any time the BIOS engineer wants the OS to see
behavior different from what the hardware actually did. They are also
triggered by timers so that the BIOS can periodically get control.
Subject: Re: UART Handling - was interrupt handshaking
From: "Maxim S. Shatskih" <firstname.lastname@example.org>
Date: Wed, 18 Dec 2002 21:39:17 +0300
> Does W2K/XP let the BIOS handle some IRQs ?
No, except SMI which IIRC can occur only on power-related transition