Subject: Re: Issue with /usr/src/sys/arch/i386/stand/lib/gatea20.c
To: Marcin Jessa <>
From: Perry E. Metzger <>
List: current-users
Date: 06/21/2005 16:47:32
David Laight <> writes:
>> No I have not but I will now. Thanks Jukka.
>> But if it works, why the heck isn't it commited?
> Because the code that is there was added for a reason - probably to
> make some other motherboard work properly.

In fact, there are a very large number of boards that require (or used
to require) the Gate A20 hack.

> Unless and until you understand the full ramifications of such a
> change, you are likely to break the boot code on some other
> platform.
> The A20 gate is a horrid hack, and it is probably difficult to find any
> reasonable amount of documentation about it.

What we might do is explicitly check whether or not the device is
there before hitting gate A20, but on the other hand I don't know if
there is an easy way to do that.

Perry E. Metzger