; A20 Wraparound check as gotten from osdev.org
check_a20_wraparound:
    pushf
    push ds
    push es
    push di
    push si

    xor ax, ax ; ax = 0
    mov es, ax

    not ax ; ax = 0xFFFF
    mov ds, ax

    mov di, 0x0500
    mov si, 0x0510

    mov al, byte [es:di]
    push ax

    mov al, byte [ds:si]
    push ax

    mov byte [es:di], 0x00
    mov byte [ds:si], 0xFF

    cmp byte [es:di], 0xFF

    pop ax
    mov byte [ds:si], al

    pop ax
    mov byte [es:di], al

    mov ax, 0
    je .exit

    mov ax, 1

.exit:
    pop si
    pop di
    pop es
    pop ds
    popf

    ret