Re: [PATCH] Loading windows in macbook

[Marco Gerards]

Bean <address@hidden> writes:

> On Wed, Jun 25, 2008 at 4:38 AM, Javier Martín <address@hidden> wrote:
>> El mié, 25-06-2008 a las 04:11 +0800, Bean escribió:
>>> 2. Macbook will halt if we disable a20, so I add a new option
>>> --keep-a20 to keep the a20 gate open.
>> Does any OS fail to boot if it has A20 enabled when it is jumped to?
>> AFAIK some BIOS even had an option to enable it at POST time, so I think
>> we should make this new option the default and have an option called
>> "--reset-a20" or something like that.
>
> I don't know of any os that would fail if a20 is enabled. Normally,
> they try to enable it as soon as possible as they need to access upper
> memory. So making it default is not a bad idea.

It's disabled for legacy reasons.  Some old DOS applications expect
addresses to wrap around.  And thus a20 gate should be disabled.

--
Marco