address@hidden: Bug#139774: GRUB hangs until A20 is not goofy :P]

[Jason Thomas]

okay more information from the bug reporter, is this a know problem, is
it fixed already?

Thanks.

----- Forwarded message from Zinx Verituse <address@hidden> -----

> Date: Sun, 24 Mar 2002 22:05:17 -0600
> From: Zinx Verituse <address@hidden>
> To: address@hidden
> Subject: Bug#139774: GRUB hangs until A20 is not goofy :P
> 
> Well, it turns out this motherboard likes to disable the keyboard
> controller completely.  Including the A20 gate.
> 
> Porting the code from Linux would fix this, as it seems to have
> some code to cover all the cases, or at least all the ones that
> matter.
> 
> For now, I've written my own gateA20 function that uses port 0x92..
> Apparently not all systems have this functionality, and some that do
> don't implement it fully (though I don't know if the problems will
> affect GRUB)
> 
> Copying from Linux (which copies from SYSLINUX) would be the best,
> I think :)
> 
> my gateA20:
> 
> /*
>  * gateA20(int linear)
>  *
>  * Gate address-line 20 for high memory.
>  *
>  * This routine will fail on some computers.
>  */
> 
> ENTRY(gateA20)
>       pushl   %eax
> 
>       inb     $0x92, %al
>       andb    $0xfe, %al
>       testb   $2, %al
>       jz      goff
> 
>       cmpl    $0, 0x8(%esp)
>       jnz     gret
> 
>       andb    $0xfc, %al
>       outb    $0x92
>       jmp     gret
> 
> goff:
>       cmpl    $0, 0x8(%esp)
>       jz      gret
> 
>       orb     $2, %al
>       outb    $0x92
> 
> gret:
>       popl    %eax
>       ret
> 
> -- 
> Zinx Verituse
> 

----- End forwarded message -----

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