;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; ;;
;; BOOTCODE.INC ;;
;; ;;
;; KolibriOS 16-bit loader, ;;
;; based on bootcode for MenuetOS ;;
;; ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;==========================================================================
;
; 16 BIT FUNCTIONS
;
;==========================================================================
putchar:
; in: al=character
mov ah, 0Eh
mov bh, 0
int 10h
ret
print:
; in: si->string
mov al, 186
call putchar
mov al, ' '
call putchar
printplain:
; in: si->string
pusha
lodsb
@@:
call putchar
lodsb
cmp al, 0
jnz @b
popa
ret
; Now int 16 is used for keyboard support.
; This is shorter, simpler and more reliable.
if 0
getkey: push ecx
push edx
add ebx,0x0101
xor eax,eax
gk1:
in al,0x60
mov cl,al
gk0:
in al,0x60
cmp al,cl
je gk0
cmp ax,11
jg gk0
gk0_1:
mov cl,al
; add al,47
; mov [ds:keyinbs-0x10000],al
; mov si,keyinbs-0x10000
; call printplain
gk12:
in al,0x60
cmp al,cl
je gk12
cmp ax,240
jne gk13
mov al,cl
jmp gk14
gk13:
add cl,128
cmp al,cl
jne gk1
sub al,128
gk14:
movzx edx,bl
cmp eax,edx
jb gk1
movzx edx,bh
cmp eax,edx
jg gk1
test ebx,0x010000
jnz gk3
mov cx,0x1000
mov dx,cx
add eax,47
mov cx,ax
cmp cx,58
jb gk_nozero
sub cx,10
gk_nozero:
mov [ds:keyin-0x10000],cl
mov si,keyin-0x10000
call printplain
gk3:
sub eax,48
pop edx
pop ecx
ret
end if
getkey:
; get number in range [bl,bh] (bl,bh in ['0'..'9'])
; in: bx=range
; out: ax=digit (1..9, 10 for 0)
mov ah, 0
int 16h
cmp al, bl
jb getkey
cmp al, bh
ja getkey
push ax
call putchar
pop ax
and ax, 0Fh
jnz @f
mov al, 10
@@:
ret
setcursor:
; in: dl=column, dh=row
mov ah, 2
mov bh, 0
int 10h
ret
macro _setcursor row,column
{
mov dx, row*256 + column
call setcursor
}
pagetable_set:
or al, 7
@@:
stosd
add eax, 1000h
loop @b
ret
; 16-bit data
; videomodes table
gr_table:
dw 0x112+0100000000000000b , 640 , 480 ; 1
dw 0x115+0100000000000000b , 800 , 600 ; 2
dw 0x118+0100000000000000b , 1024 , 768 ; 3
dw 0x11B+0100000000000000b , 1280 , 1024 ; 4
dw 0x112 , 640 , 480 ; 5
dw 0x115 , 800 , 600 ; 6
dw 0x118 , 1024 , 768 ; 7
dw 0x11B , 1280 ,1024 ; 8
dw 0x13, 320, 200 ; 9
dw 0x12, 640, 480 ; 0
; table for move to extended memory (int 15h, ah=87h)
movedesc:
db 0x00,0x00,0x0,0x00,0x00,0x00,0x0,0x0
db 0x00,0x00,0x0,0x00,0x00,0x00,0x0,0x0
db 0xff,0xff,0x0,0xa0,0x00,0x93,0x0,0x0
db 0xff,0xff,0x0,0x00,0x10,0x93,0x0,0x0
db 0x00,0x00,0x0,0x00,0x00,0x00,0x0,0x0
db 0x00,0x00,0x0,0x00,0x00,0x00,0x0,0x0
db 0x00,0x00,0x0,0x00,0x00,0x00,0x0,0x0
db 0x00,0x00,0x0,0x00,0x00,0x00,0x0,0x0
;=========================================================================
;
; 16 BIT CODE
;
;=========================================================================
start_of_code:
cld
; \begin{diamond}[02.12.2005]
cmp ax, 'KL'
jnz @f
mov word [cs:cfgmanager.loader_block-0x10000], si
mov word [cs:cfgmanager.loader_block+2-0x10000], ds
@@:
; \end{diamond}[02.12.2005]
; set up stack
mov ax, 3000h
mov ss, ax
mov sp, 0EC00h
; set up segment registers
push cs
pop ds
push cs
pop es
; set videomode
mov ax, 3
int 0x10
; Load & set russian VGA font (RU.INC)
mov bp,RU_FNT1-10000h ; RU_FNT1 - First part
mov bx,1000h ; 768 bytes
mov cx,30h ; 48 symbols
mov dx,80h ; 128 - position of first symbol
mov ax,1100h
int 10h
mov bp,RU_FNT2-10000h ; RU_FNT2 -Second part
mov bx,1000h ; 512 bytes
mov cx,20h ; 32 symbols
mov dx,0E0h ; 224 - position of first symbol
mov ax,1100h
int 10h
; End set VGA russian font
; draw frames
push 0xb800
pop es
xor di, di
; mov si,d80x25-0x10000
; mov cx,80*25
; mov ah,1*16+15
; dfl1:
; lodsb
; stosw
; loop dfl1
mov ah, 1*16+15
; draw top
mov si, d80x25_top - 0x10000
mov cx, d80x25_top_num * 80
@@:
lodsb
stosw
loop @b
; draw spaces
mov si, space_msg - 0x10000
mov cx, 25 - d80x25_top_num - d80x25_bottom_num
dfl1:
push cx
push si
mov cx, 80
@@:
lodsb
stosw
loop @b
pop si
pop cx
loop dfl1
; draw bottom
mov si, d80x25_bottom - 0x10000
mov cx, d80x25_bottom_num * 80
@@:
lodsb
stosw
loop @b
mov byte [space_msg-0x10000+80], 0 ; now space_msg is null terminated
_setcursor d80x25_top_num,0
; TEST FOR 386+
mov bx, 0x4000
pushf
pop ax
mov dx,ax
xor ax,bx
push ax
popf
pushf
pop ax
and ax,bx
and dx,bx
cmp ax,dx
jnz cpugood
mov si,not386-0x10000
sayerr:
call print
jmp $
cpugood:
; set up esp
movzx esp, sp
; FLUSH 8042 KEYBOARD CONTROLLER
;// mike.dld [
; mov al,0xED
; out 0x60,al
; or cx,-1
; @@:
; in al,0x64
; test al,2
; jz @f
; loop @b
; @@:
; mov al,0
; out 0x60,al
; or cx,-1
; @@:
; in al,0x64
; test al,2
; jz @f
; loop @b
; @@:
;// mike.dld ]
; mov ecx,10000
; fl1:
; in al,0x64
; loop fl1
; test al,1
; jz fl2
; in al,0x60
; jmp fl1
; fl2:
;****************************************************************
; The function is modified Mario79
;*****************************************************************
; wait_kbd: ; variant 1
; mov cx,2500h ;çà äåðæêà ïîðÿäêà 10 ìñåê
; test_kbd:
; in al,64h ;÷èòà åì ñîñòîÿÃèå êëà âèà òóðû
; test al,2 ;ïðîâåðêà áèòà ãîòîâÃîñòè
; loopnz test_kbd
mov al,0xf6 ; Ñáðîñ êëà âèà òóðû, ðà çðåøèòü ñêà Ãèðîâà Ãèå
out 0x60,al
xor cx,cx
wait_loop: ; variant 2
; reading state of port of 8042 controller
in al,64h
and al,00000010b ; ready flag
; wait until 8042 controller is ready
loopnz wait_loop
; DISPLAY VESA INFORMATION
push 0
pop es
mov ax,0x4f00
mov di,0xa000
int 0x10
cmp ax,0x004f
mov si, novesa-0x10000
jnz @f
mov ax,[es:di+4]
add ax,'0'*256+'0'
mov si,vervesa-0x10000
mov [si+vervesa_off], ah
mov [si+vervesa_off+2], al
@@: call print
; \begin{diamond}[30.11.2005]
cfgmanager:
; settings:
; a) preboot_graph = graphical mode
; preboot_gprobe = probe this mode?
; b) preboot_mtrr = use hardware acceleration?
; c) preboot_vrrm = use VRR?
; d) preboot_device = from what boot?
mov di, preboot_graph-0x10000
; check bootloader block
cmp [.loader_block-0x10000], 0
jz .noloaderblock
les bx, [.loader_block-0x10000]
cmp byte [es:bx], 1
mov si, loader_block_error-0x10000
jnz sayerr
test byte [es:bx+1], 1
jz @f
; image in memory present
cmp [di+preboot_device-preboot_graph], 0
jnz @f
mov [di+preboot_device-preboot_graph], 3
@@:
.noloaderblock:
; determine default settings
mov [.bSettingsChanged-0x10000], 0
cmp byte [di], 0
jnz .preboot_gr_end
mov [di+preboot_gprobe-preboot_graph], 0
mov al, [vervesa+vervesa_off-0x10000]
cmp al, 'x'
jz .novesa
cmp al, '1'
jz .vesa12
mov [di+preboot_gprobe-preboot_graph], 2
mov al, 3
jmp @f
.vesa12:
mov al, 7
jmp @f
.novesa:
mov al, 10
@@:
mov [di], al
.preboot_gr_end:
cmp [di+preboot_mtrr-preboot_graph], 1
adc [di+preboot_mtrr-preboot_graph], 0
cmp [di+preboot_vrrm-preboot_graph], 1
adc [di+preboot_vrrm-preboot_graph], 0
cmp [di+preboot_device-preboot_graph], 1
adc [di+preboot_device-preboot_graph], 0
; notify user
mov si, linef-0x10000
call print
mov si, start_msg-0x10000
call print
mov si, time_msg-0x10000
call print
; get start time
call .gettime
mov [.starttime-0x10000], eax
mov word [.timer-0x10000], .newtimer-0x10000
mov word [.timer-0x10000+2], cs
.printcfg:
_setcursor 9,0
mov si, current_cfg_msg-0x10000
call print
mov si, curvideo_msg-0x10000
call print
mov al, [preboot_graph-0x10000]
cmp al, 8
ja .pnovesa
mov dl, al
and eax, 3
mov si, [modes_msg-0x10000+eax*2]
call printplain
mov si, modevesa20-0x10000
cmp dl, 4
jbe @f
mov si, modevesa12-0x10000
@@:
call printplain
cmp dl, 4
ja .x
mov si, probeno_msg-0x10000
cmp [preboot_gprobe-0x10000], 2
jnz @f
mov si, probeok_msg-0x10000
@@:
call printplain
.x:
jmp .c
.pnovesa:
cmp al, 9
mov si, mode9-0x10000
jz @b
mov si, mode10-0x10000
jmp @b
.c:
mov si, linef-0x10000
call printplain
mov si, mtrr_msg-0x10000
cmp [preboot_mtrr-0x10000], 1
call .say_on_off
mov si, vrrm_msg-0x10000
cmp [preboot_vrrm-0x10000], 1
call .say_on_off
mov si, preboot_device_msg-0x10000
call print
mov al, [preboot_device-0x10000]
and eax, 3
mov si, [preboot_device_msgs-0x10000+eax*2]
call printplain
.wait:
_setcursor 25,0 ; out of screen
; set timer interrupt handler
cli
push 0
pop es
mov eax, [es:8*4]
mov [.oldtimer-0x10000], eax
mov eax, [.timer-0x10000]
mov [es:8*4], eax
sti
; wait for keypressed
mov ah, 0
int 16h
push ax
; restore timer interrupt
push 0
pop es
mov eax, [.oldtimer-0x10000]
mov [es:8*4], eax
mov [.timer-0x10000], eax
_setcursor 7,0
mov si, space_msg-0x10000
call printplain
pop ax
; switch on key
cmp al, 13
jz .continue
or al, 20h
cmp al, 'a'
jz .change_a
cmp al, 'b'
jz .change_b
cmp al, 'c'
jz .change_c
cmp al, 'd'
jnz .wait
_setcursor 15,0
mov si,bdev-0x10000
call print
mov bx,'13'
call getkey
mov [preboot_device-0x10000], al
_setcursor 13,0
.d:
mov [.bSettingsChanged-0x10000], 1
mov si, space_msg-0x10000
call printplain
_setcursor 15,0
mov cx, 6
@@:
call printplain
loop @b
jmp .printcfg
.change_a:
_setcursor 15,0
mov si, gr_mode-0x10000
call printplain
mov bx, '09'
call getkey
mov [preboot_graph-0x10000], al
cmp al, 4
ja @f
mov si, probetext-0x10000
call printplain
mov bx, '12'
call getkey
mov [preboot_gprobe-0x10000], al
@@:
_setcursor 10,0
jmp .d
.change_b:
_setcursor 15,0
mov si, gr_acc-0x10000
call print
mov bx, '12'
call getkey
mov [preboot_mtrr-0x10000], al
_setcursor 11,0
jmp .d
.change_c:
_setcursor 15,0
mov si, vrrmprint-0x10000
call print
mov bx, '12'
call getkey
mov [preboot_vrrm-0x10000], al
_setcursor 12,0
jmp .d
.say_on_off:
pushf
call print
mov si, on_msg-0x10000
popf
jz @f
mov si, off_msg-0x10000
@@: call printplain
ret
; novesa and vervesa strings are not used at the moment of executing this code
virtual at novesa
.oldtimer dd ?
.starttime dd ?
.bSettingsChanged db ?
.timer dd ?
end virtual
.loader_block dd 0
.gettime:
mov ah, 0
int 1Ah
xchg ax, cx
shl eax, 10h
xchg ax, dx
ret
.newtimer:
push ds
push cs
pop ds
pushf
call [.oldtimer-0x10000]
pushad
call .gettime
sub eax, [.starttime-0x10000]
sub ax, 18*5
jae .timergo
neg ax
add ax, 18-1
mov bx, 18
xor dx, dx
div bx
if lang eq ru
; ¯®¤®¦¤¨â¥ 5 ᥪã¤, 4/3/2 ᥪã¤ë, 1 ᥪã¤ã
cmp al, 5
mov cl, ' '
jae @f
cmp al, 1
mov cl, 'ã'
jz @f
mov cl, 'ë'
@@: mov [time_str+9-0x10000], cl
else
; wait 5/4/3/2 seconds, 1 second
cmp al, 1
mov cl, 's'
ja @f
mov cl, ' '
@@: mov [time_str+9-0x10000], cl
end if
add al, '0'
mov [time_str+1-0x10000], al
mov si, time_msg-0x10000
_setcursor 7,0
call print
_setcursor 25,0
popad
pop ds
iret
.timergo:
push 0
pop es
mov eax, [.oldtimer-0x10000]
mov [es:8*4], eax
mov sp, 0EC00h
.continue:
sti
_setcursor 6,0
mov si, space_msg-0x10000
call printplain
call printplain
_setcursor 6,0
mov si, loading_msg-0x10000
call print
_setcursor 15,0
cmp [.bSettingsChanged-0x10000], 0
jz .load
cmp [.loader_block-0x10000], 0
jz .load
les bx, [.loader_block-0x10000]
mov eax, [es:bx+3]
push ds
pop es
test eax, eax
jz .load
push eax
mov si, save_quest-0x10000
call print
.waityn:
mov ah, 0
int 16h
or al, 20h
cmp al, 'n'
jz .loadc
cmp al, 'y'
jnz .waityn
call putchar
mov byte [space_msg-0x10000+80], 186
pop eax
push cs
push .cont-0x10000
push eax
retf
.loadc:
pop eax
.cont:
push cs
pop ds
mov si, space_msg-0x10000
mov byte [si+80], 0
_setcursor 15,0
call printplain
_setcursor 15,0
.load:
; \end{diamond}[02.12.2005]
; ASK GRAPHICS MODE
movzx ax, [preboot_graph-0x10000]
push 0
pop es
; address is gr_table+6*(ax-1)-0x10000
add ax, ax
lea si, [gr_table-0x10000 + eax + eax*2 - 6]
mov bx,[si+0]
mov cx,[si+2]
mov dx,[si+4]
cmp al, 9*2
mov al, 32 ; BPP
jb @f
mov [es:0x9000], al
mov dword [es:0x9018], 0x800000
@@:
mov [es:0x9008],bx
mov [es:0x900A],cx
mov [es:0x900C],dx
test bh, bh
jz nov
; USE DEFAULTS OR PROBE
; bx - mode : cx - x size : dx - y size
cmp [preboot_gprobe-0x10000], 1
jz noprobe
mov bx,0x100
newprobe:
inc bx
cmp bx,0x17f
mov si,prnotfnd-0x10000
jz sayerr
probemore:
push cx
mov ax,0x4f01
mov cx,bx
and cx,0xfff
mov di,0xa000
int 0x10
pop cx
test byte [es:di], 80h ; lfb?
jz newprobe
cmp [es:di+0x12], cx ; x size?
jnz newprobe
cmp [es:di+0x14], dx ; y size?
jnz newprobe
cmp byte [es:di+0x19], 32 ;24
jb newprobe
; add bx,0100000000000000b
or bh, 40h
mov [es:0x9008],bx
noprobe:
; FIND VESA 2.0 LFB & BPP
mov ax,0x4f01
mov cx,bx
and cx,0xfff
mov di,0xa000
int 0x10
; LFB
mov eax,[es:di+0x28]
mov [es:0x9018],eax
; ---- vbe voodoo
BytesPerScanLine equ 0x10
mov ax, [es:di+BytesPerScanLine]
mov [es:0x9001],ax
; BPP
mov al,byte [es:di+0x19]
mov [es:0x9000],al
nov:
cmp al,24
mov si,bt24-0x10000
jz bppl
cmp al,32
mov si,bt32-0x10000
jz bppl
mov si,btns-0x10000
jmp sayerr
bppl:
call print
; FIND VESA 1.2 PM BANK SWITCH ADDRESS
push es
mov ax,0x4f0A
xor bx, bx
int 0x10
xor eax,eax
mov ax,es
shl eax,4
movzx ebx,di
add eax,ebx
mov bx,[es:di]
add eax,ebx
pop es
mov [es:0x9014],eax
; GRAPHICS ACCELERATION
mov al, [preboot_mtrr-0x10000]
mov [es:0x901C],al
; VRR_M USE
mov al,[preboot_vrrm-0x10000]
mov [es:0x9030],al
; MEMORY MODEL
; movzx eax,byte [es:preboot_memory-0x10000]
; cmp eax,0
; jne pre_mem
;;;;;;;;;;;;;;;;;;;;;;;;;
; mario79 - memory size ;
;;;;;;;;;;;;;;;;;;;;;;;;;
; mov ax,0E801h
;;; xor bx,bx ; thanks to Alexei for bugfix [18.07.2004]
; xor cx, cx
; xor dx, dx
; int 0x15
; movzx ebx, dx ;bx
; movzx eax, cx ;ax
; shl ebx,6 ; ïåðåâîä â êèëîáà éòû (x64)
; add eax,ebx
; add eax, 1000h ;440h
; cmp eax,40000h ; 256?
; jge mem_256_z
; cmp eax,20000h ; 128?
; jge mem_128_z
; cmp eax,10000h ; 64?
; jge mem_64_z
; cmp eax,8000h ; 32?
; jge mem_32_z
; jmp mem_16_z
;
;mem_256_z: mov si,memokz256-0x10000
; call printplain
; mov eax,5
; jmp pre_mem
;mem_128_z: mov si,memokz128-0x10000
; call printplain
; mov eax,4
; jmp pre_mem
;mem_64_z: mov si,memokz64-0x10000
; call printplain
; mov eax,3
; jmp pre_mem
;mem_32_z: mov si,memokz32-0x10000
; call printplain
; mov eax,2
; jmp pre_mem
;mem_16_z: mov si,memokz16-0x10000
; call printplain
; mov eax,1
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; pre_mem:
; push word 0x0000
; pop es
; mov [es:0x9030],al
; push word 0x1000
; pop es
; mov si,linef-0x10000
; call printplain
; DIRECT WRITE TO LFB, PAGING DISABLED
; movzx eax,byte [es:preboot_lfb-0x10000]
; mov eax,1 ; paging disabled
; cmp eax,0
; jne pre_lfb
; mov si,gr_direct-0x10000
; call printplain
; mov ebx,'12'
; call getkey
; pre_lfb:
; push word 0x0000
; pop es
; mov [es:0x901E],al
; mov ax,0x1000
; mov es,ax
; mov si,linef-0x10000
; call printplain
mov [es:0x901E],byte 1
; BOOT DEVICE
mov al, [preboot_device-0x10000]
dec al
mov [boot_dev-0x10000],al
; READ DISKETTE TO MEMORY
; cmp [boot_dev-0x10000],0
jne no_sys_on_floppy
mov si,diskload-0x10000
call print
xor ax, ax ; reset drive
xor dx, dx
int 0x13
mov cx,0x0001 ; startcyl,startsector
xor dx, dx ; starthead,drive
push word 80*2 ; read no of sect
reads:
pusha
xor si,si
newread:
mov bx,0xa000 ; es:bx -> data area
mov ax,0x0200+18 ; read, no of sectors to read
int 0x13
test ah, ah
jz goodread
inc si
cmp si,10
jnz newread
mov si,badsect-0x10000
sayerr_plain:
call printplain
jmp $
goodread:
; move -> 1mb
mov si,movedesc-0x10000
push es
push ds
pop es
mov cx,256*18
mov ah,0x87
int 0x15
pop es
test ah,ah ; was the move successfull ?
je goodmove
mov dx,0x3f2 ; floppy motor off
mov al,0
out dx,al
mov si,memmovefailed-0x10000
jmp sayerr_plain
goodmove:
add dword [movedesc-0x10000+0x18+2], 512*18
popa
inc dh
cmp dh,2
jnz bb2
mov dh,0
inc ch
pusha ; print prosentage
mov si,pros-0x10000
shr ch, 2
mov al, '5'
test ch, 1
jnz @f
mov al, '0'
@@:
mov [si+1], al
shr ch, 1
add ch, '0'
mov [si], ch
call printplain
popa
bb2:
pop ax
dec ax
push ax
jnz reads
readdone:
pop ax
mov si,backspace2-0x10000
call printplain
mov si,okt-0x10000
call printplain
no_sys_on_floppy:
xor ax, ax ; reset drive
xor dx, dx
int 0x13
mov dx,0x3f2 ; floppy motor off
mov al,0
out dx,al
push es
; PAGE TABLE
push dword [es:0x9018]
map_mem equ 64 ; amount of memory to map
push 0x6000
pop es ; es:di = 6000:0
xor di,di
mov cx,256*map_mem ; Map (mapmem) M
; mov eax,7
; pt2:
; cmp cx,256*(map_mem-8) ; 8 M map to LFB
; jnz pt3
; pop eax
; add eax,7
; pt3:
; cmp cx,256*(map_mem-12) ; 12 M back to linear = physical
; jnz pt4
; mov eax,12*0x100000 + 7
; pt4:
; stosd
; add eax,4096
; loop pt2
; initialize as identity mapping
xor eax, eax
call pagetable_set
; 8M..12M map to LFB
pop eax
; mov cx, 256*4
mov ch, 4
mov di, 2000h
call pagetable_set
push 0x7100
pop es
xor di,di
mov eax,8*0x100000
mov cx,256*4
call pagetable_set
; 4 KB PAGE DIRECTORY
push 0x7F00
pop es ; es:di = 7F00:0
xor di, di
mov cx, 64 / 4
mov eax, 0x60007 ; for 0 M
call pagetable_set
mov dword [es:0x800],0x71007 ;map region 0x80000000-0x803FFFFF to 0x800000-0xCFFFFF
xor si,si
mov di,second_base_address shr 20
mov cx,64/2
rep movs word [es:di], [es:si]
mov eax, 0x7F000 +8+16 ; Page directory and enable caches
mov cr3, eax
; SET GRAPHICS
pop es
mov ax,[es:0x9008] ; vga & 320x200
mov bx, ax
cmp ax,0x13
je setgr
cmp ax,0x12
je setgr
mov ax,0x4f02 ; Vesa
setgr:
int 0x10
test ah,ah
mov si, fatalsel-0x10000
jnz sayerr
; set mode 0x12 graphics registers:
cmp bx,0x12
jne gmok2
mov al,0x05
mov dx,0x03ce
push dx
out dx,al ; select GDC mode register
mov al,0x02
inc dx
out dx,al ; set write mode 2
mov al,0x02
mov dx,0x03c4
out dx,al ; select VGA sequencer map mask register
mov al,0x0f
inc dx
out dx,al ; set mask for all planes 0-3
mov al,0x08
pop dx
out dx,al ; select GDC bit mask register
; for writes to 0x03cf
gmok2:
push ds
pop es