title: How is BIOS ROM accessible at 0xFFFFFFF0 if A20 line is disabled by default?
body: <p>I was reading about A20 line <a href="http://wiki.osdev.org/A20_Line" rel="nofollow">http://wiki.osdev.org/A20_Line</a>, which seems to indicate that A20 line is disabled by default. On Pentium, if 0xFFFFFFF0 is the address put out immediately after hard reset, does it mean that A20 line is enabled by default? </p>