Re: That horrible hack from hell called A20

Giacomo Catenazzi
2000-12-06T13:13:59Z

"H. Peter Anvin" wrote:
>
>
> Good question. The whole thing makes me nervous... in fact, perhaps we
> should really consider using the BIOS INT 15h interrupt to enter
> protected mode?
>

Maybe it is better to try with INT15 AX=2400 (Enable A20 gate).

INT 15-2400 enable A20
INT 15-2401 disable A20
INT 15-2402 query status A20
INT 15-2403 query A20 support (kdb or port 92)

IBM classifies these functions as optional, but it is enabled on a lot
of
new BIOS, no know conflicts, thus we can call this function to enable
A20,
check the result and only after failure we can try the old methods.

giacomo