; hi_color flag is not being set yet by tseng or ATI

   include  model.h

;
;  VGAKIT Version 4.1
;
;  Copyright 1988,89,90,91 John Bridges
;  Free for use in commercial, shareware or freeware applications
;
;  BANKS.ASM
;
.data

OSEG  equ   DS:      ;segment override for variable access

bankadr  dw ?
if @Codesize
bankseg  dw ?
endif

   public   curbk

curbk dw ?

   public   vga512,vga1024

vga512   dw ?
vga1024  dw ?

   public   cirrus,everex,paradise,tseng,trident,t8900
   public   ativga,aheada,aheadb,oaktech,video7
   public   chipstech,tseng4,genoa,ncr,compaq,vesa,hi_color
   public   ati_extended          ;ati extended reg. location

cirrus   dw ?
everex   dw ?
paradise dw ?
tseng    dw ?
trident  dw ?
t8900    dw ?
ativga   dw ?
aheada   dw ?
aheadb   dw ?
oaktech  dw ?
hi_color dw ?     ; flag to indicate hi_color exists
video7   dw ?
chipstech dw   ?
tseng4   dw ?
genoa    dw ?
ncr      dw ?
compaq   dw ?
vesa     dw ?

first    dw ?     ;flag so whichvga() is only called once
retval   dw ?     ;first return value from whichvga()
ati_extended dw ? ;ati extended reg. location

vgainfo  label word
vesaid   db 'VESA'      ; 4 signature bytes
vesaver  dw ?     ; VESA version number
oemstr   dd ?     ; Pointer to OEM string
capabil  db 4 dup (?)   ; Capabilities of the video environment
modelst  dd ?     ; Pointer to supported Super VGA modes

vesashift db   0     ; number of bits to shift bank number left

.code

   public   newbank
   public   whichvga
   public   forcevga

newbank  proc        ;bank number is in AX
   cli
   mov   OSEG[curbk],ax
if @Codesize
   jmp   dword ptr OSEG[bankadr]
else
   jmp   word ptr OSEG[bankadr]
endif


_tseng:           ;Tseng
   push  ax
   push  dx
   and   al,7
   mov   ah,al
   shl   al,1
   shl   al,1
   shl   al,1
   or al,ah
   or al,01000000b
   mov   dx,3cdh
   out   dx,al
   sti
   pop   dx
   pop   ax
   ret



_tseng4:          ;Tseng 4000 series
   push  ax
   push  dx
   mov   ah,al
   mov   dx,3bfh        ;Enable access to extended registers
   mov   al,3
   out   dx,al
   mov   dl,0d8h
   mov   al,0a0h
   out   dx,al
   and   ah,15
   mov   al,ah
   shl   al,1
   shl   al,1
   shl   al,1
   shl   al,1
   or al,ah
   mov   dl,0cdh
   out   dx,al
   sti
   pop   dx
   pop   ax
   ret


_trident:         ;Trident
   push  ax
   push  dx
   mov   dx,3ceh     ;set pagesize to 64k
   mov   al,6
   out   dx,al
   inc   dl
   in al,dx
   dec   dl
   or al,4
   mov   ah,al
   mov   al,6
   out   dx,ax

   mov   dl,0c4h     ;switch to BPS mode
   mov   al,0bh
   out   dx,al
   inc   dl
   in al,dx
   dec   dl

   mov   ah,byte ptr OSEG[curbk]
   xor   ah,2
   mov   dx,3c4h
   mov   al,0eh
   out   dx,ax
   sti
   pop   dx
   pop   ax
   ret


_video7:       ;Video 7
   push  ax
   push  dx
   push  cx
   and   ax,15
   mov   ch,al
   mov   dx,3c4h
   mov   ax,0ea06h
   out   dx,ax
   mov   ah,ch
   and   ah,1
   mov   al,0f9h
   out   dx,ax
   mov   al,ch
   and   al,1100b
   mov   ah,al
   shr   ah,1
   shr   ah,1
   or ah,al
   mov   al,0f6h
   out   dx,al
   inc   dx
   in al,dx
   dec   dx
   and   al,not 1111b
   or ah,al
   mov   al,0f6h
   out   dx,ax
   mov   ah,ch
   mov   cl,4
   shl   ah,cl
   and   ah,100000b
   mov   dl,0cch
   in al,dx
   mov   dl,0c2h
   and   al,not 100000b
   or al,ah
   out   dx,al
   sti
   pop   cx
   pop   dx
   pop   ax
   ret


_paradise:        ;Paradise
   push  ax
   push  dx
   mov   dx,3ceh
   mov   ax,50fh     ;turn off write protect on VGA registers
   out   dx,ax
   mov   ah,byte ptr OSEG[curbk]
   shl   ah,1     ;change 64k bank number into 4k bank number
   shl   ah,1
   shl   ah,1
   shl   ah,1
   mov   al,9
   out   dx,ax
   sti
   pop   dx
   pop   ax
   ret


_chipstech:       ;Chips & Tech
   push  ax
   push  dx
   mov   dx,46e8h ;place chip in setup mode
   mov   ax,1eh
   out   dx,ax
   mov   dx,103h     ;enable extended registers
   mov   ax,0080h
   out   dx,ax
   mov   dx,46e8h ;bring chip out of setup mode
   mov   ax,0eh
   out   dx,ax
   mov   ah,byte ptr OSEG[curbk]
   shl   ah,1     ;change 64k bank number into 16k bank number
   shl   ah,1
   mov   al,10h
   mov   dx,3d6h
   out   dx,ax
   sti
   pop   dx
   pop   ax
   ret


_ativga:       ;ATI VGA Wonder
   push  ax
   push  dx
;  mov   dx,1ceh      this line hardcoded a changed value (Eric)
   mov   dx, [ati_extended]
   mov   ah,al
   mov   al,0b2h
   out   dx,al
   inc   dl
   in al,dx
   shl   ah,1
   and   al,0e1h
   or ah,al
   mov   al,0b2h
   dec   dl
   out   dx,ax
   sti
   pop   dx
   pop   ax
   ret


_everex:       ;Everex
   push  ax
   push  dx
   push  cx
   mov   cl,al
   mov   dx,3c4h
   mov   al,8
   out   dx,al
   inc   dl
   in al,dx
   dec   dl
   shl   al,1
   shr   cl,1
   rcr   al,1
   mov   ah,al
   mov   al,8
   out   dx,ax
   mov   dl,0cch
   in al,dx
   mov   dl,0c2h
   and   al,0dfh
   shr   cl,1
   jc nob2
   or al,20h
nob2: out   dx,al
   sti
   pop   cx
   pop   dx
   pop   ax
   ret


_aheada:       ;Ahead Systems Ver A
   push  ax
   push  dx
   push  cx
   mov   ch,al
   mov   dx,3ceh     ;Enable extended registers
   mov   ax,200fh
   out   dx,ax
   mov   dl,0cch     ;bit 0
   in al,dx
   mov   dl,0c2h
   and   al,11011111b
   shr   ch,1
   jnc   skpa
   or al,00100000b
skpa: out   dx,al
   mov   dl,0cfh     ;bits 1,2,3
   mov   al,0
   out   dx,al
   inc   dx
   in al,dx
   dec   dx
   and   al,11111000b
   or al,ch
   mov   ah,al
   mov   al,0
   out   dx,ax
   sti
   pop   cx
   pop   dx
   pop   ax
   ret


_aheadb:       ;Ahead Systems Ver A
   push  ax
   push  dx
   push  cx
   mov   ch,al
   mov   dx,3ceh     ;Enable extended registers
   mov   ax,200fh
   out   dx,ax
   mov   ah,ch
   mov   cl,4
   shl   ah,cl
   or ah,ch
   mov   al,0dh
   out   dx,ax
   sti
   pop   cx
   pop   dx
   pop   ax
   ret


_oaktech:         ;Oak Technology Inc OTI-067
   push  ax
   push  dx
   and   al,15
   mov   ah,al
   shl   al,1
   shl   al,1
   shl   al,1
   shl   al,1
   or ah,al
   mov   al,11h
   mov   dx,3deh
   out   dx,ax
   sti
   pop   dx
   pop   ax
   ret

_genoa:        ;GENOA GVGA
   push  ax
   push  dx
   mov   ah,al
   shl   al,1
   shl   al,1
   shl   al,1
   or ah,al
   mov   al,6
   or ah,40h
   mov   dx,3c4h
   out   dx,ax
   sti
   pop   dx
   pop   ax
   ret

_ncr:          ;NCR 77C22E
   push  ax
   push  dx
   shl   al,1     ;change 64k bank number into 16k bank number
   shl   al,1
   mov   ah,al
   mov   al,18h
   mov   dx,3c4h
   out   dx,ax
   mov   ax,19h
   out   dx,ax
   sti
   pop   dx
   pop   ax
   ret

_compaq:       ;Compaq
   push  ax
   push  dx
   mov   dx,3ceh
   mov   ax,50fh     ;unlock extended registers
   out   dx,ax
   mov   ah,byte ptr OSEG[curbk]
   shl   ah,1     ;change 64k bank number into 4k bank number
   shl   ah,1
   shl   ah,1
   shl   ah,1
   mov   al,45h
   out   dx,ax
   sti
   pop   dx
   pop   ax
   ret

_vesa:            ;Vesa SVGA interface
   push  ax
   push  bx
   push  cx
   push  dx
   mov   cl,[vesashift]
   shl   ax,cl
   mov   dx,ax
   xor   bx,bx
   mov   ax,4f05h
   int   10h
   sti
   pop   dx
   pop   cx
   pop   bx
   pop   ax
   ret

_nobank:
   sti
   ret

newbank  endp

bkadr macro func
   mov   [func],1
   mov   [bankadr],offset _&func
if @Codesize
   mov   [bankseg],seg _&func
endif
   endm

nojmp macro
   local lbl
	jmp   lbl
lbl:
   endm


forcevga proc vid_card:word         ;force video card to one type

	mov   [bankadr],offset _nobank   ; default for Cirrus???
if @Codesize
	mov   [bankseg],seg _nobank
endif

	mov ax, [vid_card]
	cmp   ax, 15
	jnz   no_vesa
	bkadr vesa
;	mov   [vga512],1
;	mov   [vga1024],1
	jmp   finish

no_vesa:
	cmp   ax, 1         ; ati
	jz    also_ati

	cmp   ax, 16		; ati hi_color ?
	jnz   no_ati
;	mov   [vga1024],1		; hi_color has 1 meg
also_ati:               ; ie hop into here if ati hi color
	bkadr ativga
;	mov   [vga512],1     ; forcing 512k may not exist
	jmp   finish

no_ati:     ;Test for Everex
	cmp   ax, 3
	jnz   no_ev
	bkadr everex
;	mov   [vga512],1
	jmp   finish

no_ev:         ;Test for Compaq
	cmp   ax, 14
	jnz   no_cp
	bkadr compaq
;	mov   [vga512],1
	jmp   finish

no_cp:            ;Test for NCR 77C22E
	cmp   ax, 6
	jnz   non_cr
	bkadr ncr
;	mov   [vga512],1
	jmp   finish

non_cr:        ;Test for Trident
	cmp   ax, 8
	jnz   try_8900
	bkadr trident
;	mov [vga512], 1
	jmp   finish

try_8900:                  ; test Trident 8900 assume 1 Meg
	cmp   ax, 9
	jnz   no_tri
	bkadr trident
;	mov   [vga1024],1
	jmp   finish

no_tri:     ;Test for Video 7
	cmp   ax, 12
	jnz   nov_7
	bkadr video7
;	mov   [vga1024],1
	jmp   finish

nov_7:         ;Test for GENOA GVGA
	cmp   ax, 5
	jnz   no_ci
	bkadr genoa
;	mov   [vga512],1
	jmp   finish

no_ci:         ;Test for Paradise
	cmp   ax, 7
	jnz   no_pd
	bkadr paradise
;	mov   [vga512],1
	jmp   finish

no_pd:      ;Test for Chips & Tech
	cmp   ax, 2
	jnz   no_ct
	bkadr chipstech
;	mov   [vga512],1
	jmp   finish

no_ct:
	cmp   ax, 10
	jnz   t4_mem
	bkadr tseng
;	mov   [vga512],1
	jmp   finish

t4_mem:        ;Tseng 4000 memory detect 1meg
	cmp   ax, 17      ; check for hi color mode
	jz    t4hi        ; not much to do since this does not use bank switching routine

	cmp   ax, 11
	jnz   no_ts
t4hi:
;	mov   [vga1024],1    ;full meg with eight 256kx4 RAMs
	bkadr tseng4
	jmp   finish

no_ts:
	cmp   ax, 1
	jnz   no_ab
	bkadr aheada
;	mov   [vga512],1
	jmp   finish

;verb:            ; can't force ahead b yet
;  cmp   ax,
;  bkadr aheadb
;  mov   [vga512],1
;  jmp   short finish

no_ab:         ;Test for Oak Technology
	cmp   ax, 4
	jnz   no_gn
	bkadr oaktech
;	mov   [vga512],1
	jmp   finish

no_gn:         ;Test for Cirrus


finish:
	mov	ax, 1		; always return 1 in retval ie card svga = 1
	mov   [retval],ax
	ret
forcevga endp



whichvga proc  uses si di
	local vesabuf[256]:byte

	cmp   [first],'FI'
	jnz   gotest
	mov   ax,[retval]
	ret
gotest:  mov   [bankadr],offset _nobank
if @Codesize
   mov   [bankseg],seg _nobank
endif
	xor   ax,ax
   mov   [curbk],ax
   mov   [vga512],ax
   mov   [vga1024],ax
   mov   [cirrus],ax
   mov   [everex],ax
	mov   [paradise],ax
   mov   [tseng],ax
   mov   [trident],ax
   mov   [t8900],ax
	mov   [ativga],ax
   mov   [aheada],ax
	mov   [aheadb],ax
	mov   [oaktech],ax
	mov   [video7],ax
	mov   [chipstech],ax
	mov   [tseng4],ax
	mov   [genoa],ax
	mov   [ncr],ax
	mov   [compaq],ax
	mov   [vesa],ax
	mov   [first],'FI'

	mov   ax,ss
	mov   es,ax
	lea   di,vesabuf[0]
	mov   ax,4f00h
	int   10h
	cmp   ax,4fh
	jnz   novesa
	lea   si,vesabuf[0]
	mov   di,offset vgainfo
	mov   ax,ds
	mov   es,ax
	push  ds
	mov   ax,ss
	mov   ds,ax
	mov   cx,7
	cld
	rep   movsw
	pop   ds
	bkadr vesa
	mov   [vga512],1
	mov   [vga1024],1
	jmp   fini

novesa:  mov   si,1
	mov   ax,0c000h
	mov   es,ax
	cmp   word ptr es:[40h],'13'  ;ATI Signiture on the Video BIOS
	jnz   noati
	bkadr ativga

	mov   ax, 0c000h     ; find the location of the ATI extended reg
	mov   es, ax
	mov   bx, 10h
	mov   dx, es:[bx] ; fetch the extended reg value
	mov   [ati_extended], dx

	cli
	mov   dx,1ceh
	mov   al,0bbh
	out   dx,al
	inc   dl
	in    al,dx
	sti
   and   al,20h
   jz    no512
	mov   [vga512],1
no512:
      jmp   fini

noati:   mov   ax,7000h    ;Test for Everex
   xor   bx,bx
	cld
   int   10h
   cmp   al,70h
   jnz   noev
	bkadr everex
   and   ch,11000000b      ;how much memory on board
	jz skp
   mov   [vga512],1
skp:              ;fall through for Everex boards using Trident or Tseng4000

noev: mov   ax,0bf03h      ;Test for Compaq
   xor   bx,bx
   mov   cx,bx
   int   10h
   cmp   ax,0bf03h
   jnz   nocp
   test  cl,40h         ;is 640x480x256 available?
   jz nocp
   bkadr compaq
   mov   [vga512],1
   jmp   fini

nocp: mov   dx,3c4h        ;Test for NCR 77C22E
   mov   ax,0ff05h
	call  _isport2
   jnz   noncr
   mov   ax,5        ;Disable extended registers
   out   dx,ax
   mov   ax,0ff10h      ;Try to write to extended register 10
   call  _isport2    ;If it writes then not NCR
   jz noncr
   mov   ax,105h        ;Enable extended registers
   out   dx,ax
   mov   ax,0ff10h
	call  _isport2
   jnz   noncr       ;If it does NOT write then not NCR
   bkadr ncr
	mov   [vga512],1
	jmp   fini

noncr:   mov   dx,3c4h        ;Test for Trident
   mov   al,0bh
   out   dx,al
   inc   dl
   in al,dx
   cmp   al,06h
   ja notri
   cmp   al,2
   jb notri
	bkadr trident
   cmp   al,3
   jb no89
   mov   [t8900],1
   mov   dx,3d5h
   mov   al,1fh
   out   dx,al
	inc   dx
	in al,dx
	and   al,3
	cmp   al,1
	jb notmem
	mov   [vga512],1
	je notmem
	mov   [vga1024],1
notmem:  jmp   fini

no89: mov   [vga512],1
	jmp   fini

notri:   mov   ax,6f00h    ;Test for Video 7
   xor   bx,bx
   cld
	int   10h
   cmp   bx,'V7'
   jnz   nov7
   bkadr video7
   mov   ax,6f07h
   cld
   int   10h
   and   ah,7fh
	cmp   ah,1
   jbe   skp2
   mov   [vga512],1
skp2: cmp   ah,3
   jbe   skp3
   mov   [vga1024],1
skp3: jmp   fini

nov7: mov   dx,3d4h        ;Test for GENOA GVGA
   mov   ax,032eh    ;check for Herchi Register
	call  _isport2
   jnz   nogn
	mov   dx,3c4h        ;check for memory segment register
   mov   ax,3f06h
   call  _isport2
   jnz   nogn
   bkadr genoa
   mov   [vga512],1
   jmp   fini

nogn: call  _cirrus        ;Test for Cirrus
   cmp   [cirrus],0
	je noci
   jmp   fini

noci: mov   dx,3ceh        ;Test for Paradise
	mov   al,9        ;check Bank switch register
   out   dx,al
   inc   dx
   in al,dx
   dec   dx
   or al,al
   jnz   nopd

   mov   ax,50fh        ;turn off write protect on VGA registers
   out   dx,ax
   mov   dx,offset _pdrsub
   mov   cx,1
   call  _chkbk
   jc nopd        ;if bank 0 and 1 same not paradise
   bkadr paradise
   mov   dx,3ceh
   mov   al,0bh         ;512k detect from Bob Berry
	out   dx,al
	inc   dx
   in al,dx
	test  al,80h         ;if top bit set then 512k
   jz nop512
   mov   [vga512],1
nop512:  jmp   fini

nopd: mov   ax,5f00h    ;Test for Chips & Tech
   xor   bx,bx
   cld
   int   10h
	cmp   al,5fh
	jnz   noct
   bkadr chipstech
   cmp   bh,1
   jb skp4
	mov   [vga512],1
skp4: jmp   fini

noct: mov   ch,0
   mov   dx,3d4h        ;check for Tseng 4000 series
   mov   ax,0f33h
   call  _isport2
   jnz   not4
   mov   ch,1

   mov   dx,3bfh        ;Enable access to extended registers
   mov   al,3
   out   dx,al
   mov   dx,3d8h
   mov   al,0a0h
   out   dx,al
   jmp   short yes4

not4: mov   dx,3d4h        ;Test for Tseng 3000 or 4000
   mov   ax,1f25h    ;is the Overflow High register there?
	call  _isport2
   jnz   nots
   mov   al,03fh        ;bottom six bits only
   jmp   short yes3
yes4: mov   al,0ffh
yes3: mov   dx,3cdh        ;test bank switch register
	call  _isport1
   jnz   nots
   bkadr tseng
   cmp   ch,0
	jnz   t4mem
   mov   [vga512],1
   jmp   fini

t4mem:   mov   dx,3d4h        ;Tseng 4000 memory detect 1meg
   mov   al,37h
   out   dx,al
   inc   dx
	in al,dx
   test  al,1000b    ;if using 64kx4 RAMs then no more than 256k
   jz nomem
   and   al,3
   cmp   al,1        ;if 8 bit wide bus then only two 256kx4 RAMs
   jbe   nomem
   mov   [vga512],1
   cmp   al,2        ;if 16 bit wide bus then four 256kx4 RAMs
   je nomem
   mov   [vga1024],1    ;full meg with eight 256kx4 RAMs
nomem:   bkadr tseng4
   jmp   short fini

nots:
   mov   dx,3ceh        ;Test for Above A or B chipsets
   mov   ax,200fh
	out   dx,ax
   inc   dx
   nojmp
   in al,dx
   cmp   al,21h
   jz verb
   cmp   al,20h
   jnz   noab
   bkadr aheada
   mov   [vga512],1
	jmp   short fini

verb: bkadr aheadb
   mov   [vga512],1
	jmp   short fini

noab: mov   dx,3deh        ;Test for Oak Technology
   mov   ax,0ff11h      ;look for bank switch register
   call  _isport2
   jnz   nooak
   bkadr oaktech
   mov   al,0dh
   out   dx,al
   inc   dx
   nojmp
   in al,dx
   test  al,80h
	jz no4ram
	mov   [vga512],1
no4ram:  jmp   short fini

nooak:   mov   si,0

fini: mov   ax,si
	mov   [retval],ax
	ret
whichvga endp


_cirrus  proc  near
	mov   dx,3d4h     ; assume 3dx addressing
	mov   al,0ch      ; screen a start address hi
	out   dx,al    ; select index
	inc   dx    ; point to data
	mov   ah,al    ; save index in ah
	in al,dx    ; get screen a start address hi
	xchg  ah,al    ; swap index and data
	push  ax    ; save old value
	push  dx    ; save crtc address
	xor   al,al    ; clear crc
	out   dx,al    ; and out to the crtc

	mov   al,1fh      ; Eagle ID register
	dec   dx    ; back to index
	out   dx,al    ; select index
	inc   dx    ; point to data
	in al,dx    ; read the id register
	mov   bh,al    ; and save it in bh

   mov   cl,4     ; nibble swap rotate count
   mov   dx,3c4h     ; sequencer/extensions
   mov   bl,6     ; extensions enable register

   ror   bh,cl    ; compute extensions disable value
   mov   ax,bx    ; extensions disable
   out   dx,ax    ; disable extensions
   inc   dx    ; point to data
   in al,dx    ; read enable flag
   or al,al    ; disabled ?
   jnz   exit     ; nope, not an cirrus

   ror   bh,cl    ; compute extensions enable value
   dec   dx    ; point to index
   mov   ax,bx    ; extensions enable
   out   dx,ax    ; enable extensions
   inc   dx    ; point to data
   in al,dx    ; read enable flag
   cmp   al,1     ; enabled ?
   jne   exit     ; nope, not an cirrus
   mov   [cirrus],1
   mov   [bankadr],offset _nobank
if @Codesize
   mov   [bankseg],seg _nobank
endif
exit: pop   dx    ; restore crtc address
   dec   dx    ; point to index
   pop   ax    ; recover crc index and data
   out   dx,ax    ; restore crc value
   ret
_cirrus  endp

_chkbk   proc  near     ;bank switch check routine
   mov   di,0b800h
   mov   es,di
   xor   di,di
   mov   bx,1234h
   call  _gochk
   jnz   badchk
   mov   bx,4321h
   call  _gochk
   jnz   badchk
   clc
   ret
badchk:  stc
   ret
_chkbk   endp

_gochk   proc  near
   push  si
   mov   si,bx

   mov   al,cl
   call  dx
   xchg  bl,es:[di]
   mov   al,ch
   call  dx
   xchg  bh,es:[di]

   xchg  si,bx

   mov   al,cl
   call  dx
   xor   bl,es:[di]
   mov   al,ch
   call  dx
   xor   bh,es:[di]

   xchg  si,bx

   mov   al,ch
   call  dx
   mov   es:[di],bh
   mov   al,cl
   call  dx
   mov   es:[di],bl

   mov   al,0
   call  dx
   or si,si
   pop   si
   ret
_gochk   endp


_pdrsub  proc  near     ;Paradise
   push  dx
   mov   ah,al
   mov   dx,3ceh
   mov   al,9
   out   dx,ax
   pop   dx
   ret
_pdrsub  endp


_isport2 proc  near
   push  bx
   mov   bx,ax
   out   dx,al
   mov   ah,al
   inc   dx
   in al,dx
   dec   dx
   xchg  al,ah
   push  ax
   mov   ax,bx
   out   dx,ax
   out   dx,al
   mov   ah,al
   inc   dx
   in al,dx
   dec   dx
   and   al,bh
   cmp   al,bh
   jnz   noport
   mov   al,ah
   mov   ah,0
   out   dx,ax
   out   dx,al
   mov   ah,al
   inc   dx
   in al,dx
   dec   dx
   and   al,bh
   cmp   al,0
noport:  pop   ax
   out   dx,ax
   pop   bx
   ret
_isport2 endp

_isport1 proc  near
   mov   ah,al
   in al,dx
   push  ax
   mov   al,ah
   out   dx,al
   in al,dx
   and   al,ah
   cmp   al,ah
   jnz   noport2
   mov   al,0
   out   dx,al
   in al,dx
   and   al,ah
   cmp   al,0
noport2: pop   ax
   out   dx,al
   ret
_isport1 endp

   end