Re: That horrible hack from hell called A20

From: Giacomo Catenazzi (cate@student.ethz.ch)
Date: Wed Dec 06 2000 - 07:43:08 EST


"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
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