If BIOS starts writing to port 0x80 after reset what happens? My
chipset is Intel 82945/82801GR or 945/ICH7R.

Does the north bridge , 945, routes the request to the south bridge,
ICH7? What happens from a hardware point of view? (Will this request
be advertised on every bus?)
Posted on 2010-07-04 02:29:46 by logicman112
It strictly depends on the MCH/ICH config. You need to read their respective specs. IIRC, by default MCHs/ICHs are in something like "legacy mode" until you configure them otherwise.
Posted on 2010-07-04 10:10:12 by ti_mo_n
The first instruction is out %al, 0x80!
Suppose, if MCH/ICH was not configured and CPU executes the instruction above...
Posted on 2010-07-05 02:01:12 by logicman112