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The NMI normally doesn't fire that often, but if the computer has some weird hardware or BIOS crap, that might be an issue.

Hi,
1 - Im booting from a cd-rw.
2 - I try to disable the NMI, didnt work.
3 - I put the code, from wiki, to enable A20 and the computer start to beep!
4 - I put a "breakpoint" on the code and i saw that the code reset after a write to cr0.
Any Ideias?

Thanks,
Ângelo

How old is the computer? If it's over 20 years old, it won't have a 386 or higher, but that's seriously unlikely.

Hi, its a celeron.
I did the following modifications...it worked...

1- org 0x07c00
2- end_gdt - gdt - 1
3- bits 16 after the start label
4- mov ax, 0x0000
mov ds, ax
mov ss, ax before entering Protected mode.

thanks,
Ângelo

That would be the problem, having no segment registers set up. Never assume the BIOS sets them up for you.

Hi, the biggest problem was in the org directive...and i dont understand why...
When i put org 0x07c0 or 0x7c0 it didnt work, only when i put 0x07c00.
Any ideias?
Thanks,
Ângelo

mobruan wrote:Hi, the biggest problem was in the org directive...and i dont understand why...
When i put org 0x07c0 or 0x7c0 it didnt work, only when i put 0x07c00.
Any ideias?
Thanks,
Ângelo

That's because 0x7c0 and 0x7c00 are different numbers.

Is your problem a bit solved now or completely?
It's logical that it is only working with 0x7C00 because your bootstrap gets loaded to 0x0000:0x7C00 and not anywhere else.
Maybe some bioses would load it somewhere else, but that's not the point here.
In your posted code, you already had used ORG 0x7C00, why do you changed it?