;旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� ;� PMode Tutorial (c) 1996 MATTsoft, All rights reserved. � ;쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� ;� THiS iS EXAMPLE (4th) Switch to Pmode, setup GDTR and write to screen '?' � ;� 頰頰頰頰頰頰� G00D LuCK! 頰頰頰頰頰頰� � ;읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� ; ������������� IMPORTANT �������������� ; 栢栢栢栢 Select your gr. card 栢栢栢栢 VIDEO_SEG equ 0B0000h ; for HERCULES ;VIDEO_SEG equ 0B8000h ; for VGA ; 栢栢栢栢栢栢栢栢栢栢栢栢栢栢栢栢栢栢栢 LOCALS @@ ;袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴 CODE SEGMENT BYTE PUBLIC 'CODE' ASSUME CS:CODE,DS:DATA .386 .386P ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 Start: mov ax,DATA mov ds,ax mov es,ax ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 call CheckProcessor ; Check if 386+ call CheckV86 ; Check V86 mode call EnableA20 ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 ASSUME DS:DATA32 ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 xor eax,eax mov ax,DATA32 mov ds,ax ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 shl eax,4 add dword ptr ds:[GDT+2],eax ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 lgdt fword ptr ds:[GDT] ; Load GDTR mov eax,cr0 or al,1 mov cr0,eax ; Set Pmode mov ax,CORE32_idx mov ds,ax ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 mov ebx,VIDEO_SEG add ebx,320 mov word ptr ds:[ebx],'??' ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 mov eax,cr0 xor al,1 mov cr0,eax ; Return back to real :-( ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 mov ax,4c00h int 21h ; ... and terminate ;컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 ; $0ME R0UTiNES... ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 ; Checks if the processor is 386+ CheckProcessor: pushf ; save flags for later xor ah,ah ; clear high byte push ax ; push AX on the stack popf ; pop this value into the flag register pushf ; push flags on the stack pop ax ; ...and get flags into AX and ah,0f0h ; try to set the high nibble cmp ah,0f0h ; on a 80386, the high nibble can never be 0f0h je @@1 ; ... mov ah,70h ; now try to set NT and IOPL push ax ; popf ; pushf ; pop ax ; and ah,70h ; if they couldn't be modified, no 386 is installed jz @@1 ; ... popf ; restore flags retn ; and return @@1: mov dx,offset no386err ; if there is no 386, exit with error msg mov ah,9 int 21h mov ax,4c01h int 21h ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 ; Checks if in V86 mode CheckV86: smsw ax ; mov eax,cr0 is not allowed in V86 test al,1 ; Test for V86 jnz @@1 ret @@1: mov dx,offset InV86err ; if in V86, exit with error msg mov ah,9 int 21h mov ax,4c02h int 21h ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 ; Enable A20 gate EnableA20: mov ah,11011111b call GateA20 or al,al jnz @@1 ret @@1: mov dx,offset A20err mov ah,9 int 21h mov ax,4C03h int 21h GateA20:cli call @@2 jnz @@1 mov al,0d1h out 64h,al call @@2 jnz @@1 mov al,ah out 60h,al call @@2 @@1: ret @@2: push cx sub cx,cx @@3: in al,64h and al,00000010b loopnz @@3 pop cx ret ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 CODE ENDS ;袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴 DATA SEGMENT PARA PUBLIC 'DATA' USE16 ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 ; Error messages no386err db '386 is needed!',13,10,'$' InV86err db 'Processor is in V86 mode!',13,10,'$' A20err db 'A20 error!!!',13,10,'$' DATA ENDS ;袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴 DATA32 SEGMENT PARA PUBLIC 'DATA32' USE32 ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 ; Global Descriptor Table GDT dw GDT_Size ; Limit[0..15] dd offset GDT_0 ; Base[0..32] ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 GDT_0 dw 0 ; Limit[0..15] db 0,0,0 ; Base[0..23] db 0 ; AR[] db 0 ; Info[] db 0 ; Base[24..31] ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 GDT_Core32 dw 0ffffh ; Limit[0..15] db 0,0,0 ; Base[0..23] db 10010010b ; AR[P=1,DPL=0,ED=0,W=1,A=0] db 11001111b ; Info[G=1,s=1], Limit[16..19] db 0 ; Base[24..31] ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 GDT_Size = ($-GDT_0) ;沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆沆 CORE32_idx = 08h DATA32 ENDS ;袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴袴 END