;=----------------------------------------------------------------------------=;
;                            GNU GPL OS/K                                      ;
;                                                                              ;
;   Authors: spectral`                                                         ;
;            NeoX                                                              ;
;                                                                              ;
;   Desc:   Basic realmode CPU Detection                                       ;
;                  (x86_64 architecture only)                                  ;
;=----------------------------------------------------------------------------=;

[BITS 16]

;; GLOBAL DATA
NoLongMode      db   0x0A, 0x0D, "ERROR : Your computer is not designed for x64 OS", 0

;; TEXT

Is64bits:
;-----------------------------------------------------------------------;
; Checks if the CPU is compatible with 64-bits operating systems        ;
; If the 21th bit of the eax register is set, then CPUID is supported   ;
; We then test CPUID's result to see if long mode is supported          ;
;-----------------------------------------------------------------------;
    pushfd                                  ; recovering the flags in eax
    pop eax
    mov ecx, eax
    xor eax, 0x200000
    push eax
    popfd
    pushfd
    pop eax
    xor eax, ecx
    shr eax, 21
    and eax, 1                              ; magical spell of murta
    push ecx
    popfd
    test eax, eax
    jz .NonCompat                           ; if (CPUID non supporté) goto NonCompat
    mov eax, 0x80000000
    cpuid
    cmp eax, 0x80000001
    jb .NonCompat                           ; if (eax <= 0x80000001) goto NonCompat
    mov eax, 0x80000001
    cpuid
    test edx, 1 << 29
    jz .NonCompat                           ; if (edx != 1 << 29) goto NonCompat
    ret                                     ; back to mbr.s
.NonCompat:
    stc
    ret