;----------------------------------------------------------------------------- ; CPU_Type determines the CPU type in the system. ;----------------------------------------------------------------------------- ; Written by: ; Robert Collins ; 3361 Keys Lane ; Anaheim, CA 92804 ;----------------------------------------------------------------------------- ; Input: None ; Output: AX = CPU type ; 0 = 8086/8088 ; 1 = 80186/80188 ; 2 = 80286 ; 3 = 80386 ; 4 = 80486 ; FFFF = Unknown CPU type ;----------------------------------------------------------------------------- .radix 16 ; anybody that programs in base 10 is a wimp! .386P ; MASM 5.1 directive ;----------------------------------------------------------------------------- ; PUBLIC statements here ;----------------------------------------------------------------------------- Public CPU_Type ;----------------------------------------------------------------------------- ; Local variable definitions ;----------------------------------------------------------------------------- INT6 equ [bp-4] ;----------------------------------------------------------------------------- ; Interrupt vector segment ;----------------------------------------------------------------------------- ABS0 segment use16 at 0 org 6*4 Orig_INT6 dd ? ABS0 ends ;----------------------------------------------------------------------------- ; 80486 instruction macro -- because MASM 5.1 doesn't support the 80486! ;----------------------------------------------------------------------------- XADD macro db 0fh,0C0h,0D2h ; 80486 instruction macro ENDM cseg segment para use16 public 'code' assume cs:cseg CPU_Type proc near ;----------------------------------------------------------------------------- ; Determine the CPU type by testing for differences in the CPU in the system. ;----------------------------------------------------------------------------- ; To test for the 8086/8088, test the value of SP after it is placed on the ; stack. The 8086/8088 increments this value before pushing it on the stack, ; all other CPU's increment SP after pushing it on the stack. ;----------------------------------------------------------------------------- xor ax,ax ; clear CPU type return register push sp ; save SP on stack to look at pop bx ; get SP saved on stack cmp bx,sp ; if 8086/8088, these values will differ jnz CPU_8086_exit ; yep ;----------------------------------------------------------------------------- ; When we get here, we know that we aren't a 8086/8088. And since all ; subsequent processors will trap invalid opcodes via INT6, we will determine ; which CPU we are by trapping an invalid opcode. ; We are an 80486 if: XADD DX,DX executes correctly ; 80386 if: MOV EDX,CR0 executes correctly ; 80286 if: SMSW DX executes correctly ; 80186 if: SHL DX,5 executes correctly ;----------------------------------------------------------------------------- ; Setup INT6 handler ;----------------------------------------------------------------------------- enter 4,0 ; create stack frame mov word ptr INT6,offset INT6_handler mov INT6+2,cs call set_INT6_vector ; set pointer to our INT6 handler mov ax,4 ; initialize CPU flag=4 (80486) xor cx,cx ; initialize semaphore ;----------------------------------------------------------------------------- ; Now, try and determine which CPU we are by executing invalid opcodes. ; The instructions I chose to invoke invalid opcodes, are themselves rather ; benign. In each case, the chosen instruction modifies the DX register, ; and nothing else. No system parameters are changed, e.g. protected mode, ; or other CPU dependant features. ;----------------------------------------------------------------------------- ; The 80486 instruction 'XADD' xchanges the registers, then adds them. ; The exact syntax for a '486 compiler would be: XADD DX,DX. ;----------------------------------------------------------------------------- XADD ;DX,DX ; 80486 jcxz CPU_exit dec ax ; set 80386 semaphore inc cx ; CX=0 ;----------------------------------------------------------------------------- ; For a description on the effects of the following instructions, look in ; the Intel Programmers Reference Manual's for the 80186, 80286, or 80386. ;----------------------------------------------------------------------------- mov edx,cr0 ; 80386 jcxz CPU_exit dec ax ; set 80286 semaphore inc cx ; CX=0 smsw dx ; 80286 jcxz CPU_exit dec ax ; set 80186 semaphore inc cx ; CX=0 shl dx,5 ; 80186/80188 jcxz CPU_exit dec ax ; set UNKNOWN_CPU semaphore CPU_exit: call set_INT6_vector leave CPU_8086_exit: ret ;----------------------------------------------------------------------------- ; Set the INT6 vector by exchanging it with the one currently on the stack. ;----------------------------------------------------------------------------- set_INT6_vector: push ds push ABS0 ; save interrupt vector segment pop ds ; make DS=INT vector segment mov dx,word ptr ds:Orig_INT6; ; get offset if INT6 handler xchg INT6,dx ; set new INT6 offset mov word ptr ds:Orig_INT6,dx mov dx,word ptr ds:Orig_INT6+2 ; get segment of INT6 handler xchg INT6+2,dx ; set new INT6 segment mov word ptr ds:Orig_INT6+2,dx pop ds ; restore segment register ret ; split ;----------------------------------------------------------------------------- ; INT6 handler sets a semaphore (CX=FFFF) and adjusts the return address to ; point past the invalid opcode. ;----------------------------------------------------------------------------- INT6_handler: enter 0,0 ; create new stack frame dec cx ; make CX=FFFF add word ptr ss:[bp][2],3 ; point past invalid opcode leave iret CPU_Type endp cseg ends end -- "Worship the Lord your God, and serve him only." Mat. 4:10 Robert Collins UUCP: ucbvax!ucivax!icnvax!conexch!rob HOMENET: (805) 523-3205 UUCP: uunet!ccicpg!turnkey!conexch!rob WORKNET: (805) 378-7901