[BITS 16]
[ORG 0x7c00]
start:
    mov ah,0x00 ; set mode
    mov al,0x03 ; set vga text buffer mode (80x25)
    int 0x10    ; call bios

    cli

    in al, 0x92
    or al, 2
    out 0x92, al

    xor ax, ax
    mov ds, ax

    lgdt [GDT_PTR]

    mov eax, 0x11
    mov cr0, eax
    jmp GDT_BOOT_CS-GDT:protmode

[BITS 32]
protmode:
    mov ax, GDT_BOOT_DS-GDT
    mov ds, ax
    mov ss, ax
    mov es, ax
    mov esp, 0x90000 ; temporary stack

    mov edi, 0xb8000
    mov eax, "P R "
    stosd

hang:
    pause
    jmp hang

GDT_PTR:
    dw GDT_END-GDT-1
    dd GDT


align 16
GDT:

    GDT_NULL: dq 0 ; segment zero cannot be used
    GDT_BOOT_DS: dq 0X00CF92000000FFFF
    GDT_BOOT_CS: dq 0X00CF9A000000FFFF

    GDT_END:

times 510-$+start db 0;
db 0x55;
db 0xaa;