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Dalibor Marković
2026-05-29 00:39:46 +02:00
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Computer hardware/VGA documents/VGABIOS.TXT
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----------1000-------------------------------
INT 10 - VIDEO - SET VIDEO MODE
AH = 00h
AL = mode (see below)
Return: AL = video mode flag (Phoenix BIOS)
20h mode > 7
30h modes <= 7 except mode 6
3Fh mode 6
AL = CRT controller mode byte (Phoenix 386 BIOS v1.10)
Note: IBM standard modes do not clear the screen if the high bit of AL is set
(EGA or higher only)
Values for video mode:
text/ text pixel pixel colors display scrn system
grph resol box resoltn pages addr
00h = T 40x25 8x14 16gray 8 B800 EGA
= T 40x25 8x16 16 8 B800 MCGA
= T 40x25 9x16 16 8 B800 VGA
01h = T 40x25 8x14 16 8 B800 EGA
= T 40x25 8x16 16 8 B800 MCGA
= T 40x25 9x16 16 8 B800 VGA
02h = T 80x25 8x14 16gray 4 B800 EGA
= T 80x25 8x16 16 4 B800 MCGA
= T 80x25 9x16 16 4 B800 VGA
03h = T 80x25 8x14 16 4 B800 EGA
= T 80x25 8x16 16 4 B800 MCGA
= T 80x25 9x16 16 4 B800 VGA
04h = G 40x25 8x8 320x200 4 B800 CGA,PCjr,EGA,MCGA,VGA
05h = G 40x25 8x8 320x200 4gray B800 CGA,PCjr,EGA
= G 40x25 8x8 320x200 4 B800 MCGA,VGA
06h = G 80x25 8x8 640x200 2 B800 CGA,PCjr,EGA,MCGA,VGA
07h = T 80x25 9x14 mono var B000 MDA,Hercules,EGA
= T 80x25 9x16 mono B000 VGA
0Bh = reserved (used internally by EGA BIOS)
0Ch = reserved (used internally by EGA BIOS)
0Dh = G 40x25 8x8 320x200 16 8 A000 EGA,VGA
0Eh = G 80x25 8x8 640x200 16 4 A000 EGA,VGA
0Fh = G 80x25 8x14 640x350 mono 2 A000 EGA,VGA
10h = G 80x25 8x14 640x350 4 2 A000 64k EGA
= G 640x350 16 A000 256k EGA,VGA
11h = G 80x30 8x16 640x480 mono A000 VGA,MCGA,ATI EGA,ATI VIP
12h = G 80x30 8x16 640x480 16/256k A000 VGA,ATI VIP
= G 80x30 8x16 640x480 16/64 A000 ATI EGA Wonder
13h = G 40x25 8x8 320x200 256/256k A000 VGA,MCGA,ATI VIP
----------1001-------------------------------
INT 10 - VIDEO - SET TEXT-MODE CURSOR SHAPE
AH = 01h
CH = bit 7 should be zero
bits 6,5 cursor blink
(00=normal, 01=invisible, 10=erratic, 11=slow)
(00=normal, other=invisible on EGA/VGA)
bits 4-0 top scan line containing cursor
CL = bottom scan line containing cursor (bits 0-4)
Notes: buggy on EGA systems--BIOS remaps cursor shape in 43 line modes, but
returns unmapped cursor shape
applications which wish to change the cursor by programming the
hardware directly on EGA or above should call INT 10/AX=1130h or
read 0040h:0085h first to determine the current font height
BUG: AMI 386 BIOS and AST Premier 386 BIOS will lock up the system if AL
is not equal to the current video mode
----------1002-------------------------------
INT 10 - VIDEO - SET CURSOR POSITION
AH = 02h
BH = page number
0-3 in modes 2&3
0-7 in modes 0&1
0 in graphics modes
DH = row (00h is top)
DL = column (00h is left)
----------1003-------------------------------
INT 10 - VIDEO - GET CURSOR POSITION AND SIZE
AH = 03h
BH = page number
0-3 in modes 2&3
0-7 in modes 0&1
0 in graphics modes
Return: AX = 0000h (Phoenix BIOS)
CH = start scan line
CL = end scan line
DH = row (00h is top)
DL = column (00h is left)
Notes: a separate cursor is maintained for each of up to 8 display pages
many ROM BIOSes incorrectly return the default size for a color display
(start 06h, end 07h) when a monochrome display is attached
----------1004-------------------------------
INT 10 - VIDEO - READ LIGHT PEN POSITION (EGA Only)
AH = 04h
Return: AH = light pen trigger flag
00h not down/triggered
01h down/triggered
DH,DL = row,column of character light pen is on
CH = pixel row (graphics modes 04h-06h)
CX = pixel row (graphics modes with >200 rows)
BX = pixel column
Notes: on a CGA, returned column numbers are always multiples of 2 (320-
column modes) or 4 (640-column modes)
returned row numbers are only accurate to two lines
----------1005-------------------------------
INT 10 - VIDEO - SELECT ACTIVE DISPLAY PAGE
AH = 05h
AL = new page number (00h to number of pages - 1) (see AH=00h)
----------1006-------------------------------
INT 10 - VIDEO - SCROLL UP WINDOW
AH = 06h
AL = number of lines by which to scroll up (00h = clear entire window)
BH = attribute used to write blank lines at bottom of window
CH,CL = row,column of window's upper left corner
DH,DL = row,column of window's lower right corner
Note: affects only the currently active page (see AH=05h)
Warning: some implementations have a bug which destroys BP
----------1007-------------------------------
INT 10 - VIDEO - SCROLL DOWN WINDOW
AH = 07h
AL = number of lines by which to scroll down (00h=clear entire window)
BH = attribute used to write blank lines at top of window
CH,CL = row,column of window's upper left corner
DH,DL = row,column of window's lower right corner
Note: affects only the currently active page (see AH=05h)
Warning: some implementations have a bug which destroys BP
----------1008-------------------------------
INT 10 - VIDEO - READ CHARACTER AND ATTRIBUTE AT CURSOR POSITION
AH = 08h
BH = page number (00h to number of pages - 1) (see AH=00h)
Return: AH = attribute
bit 7: blink
bits 6-4: background color
000 black
001 blue
010 green
011 cyan
100 red
101 magenta
110 brown
111 white
bits 3-0: foreground color
0000 black 1000 dark grey
0001 blue 1001 light blue
0010 green 1010 light green
0011 cyan 1011 light cyan
0100 red 1100 light red
0101 magenta 1101 light magenta
0110 brown 1110 yellow
0111 light grey 1111 white
AL = character
Notes: for monochrome displays, a foreground of 1 with background 0 is
underlined the blink bit may be reprogrammed to enable intense
background colors using AX=1003h or by programming the CRT controller
----------1009-------------------------------
INT 10 - VIDEO - WRITE CHARACTER AND ATTRIBUTE AT CURSOR POSITION
AH = 09h
AL = character to display
BH = page number (00h to number of pages - 1) (see AH=00h)
BL = attribute (text mode) or color (graphics mode)
if bit 7 set in graphics mode, character is xor'ed onto screen
CX = number of times to write character
Notes: all characters are displayed, including CR, LF, and BS
replication count in CX may produce an unpredictable result in graphics
modes if it is greater than the number of positions remaining in the
current row
----------100A-------------------------------
INT 10 - VIDEO - WRITE CHARACTER ONLY AT CURSOR POSITION
AH = 0Ah
AL = character to display
BH = page number (00h to number of pages - 1) (see AH=00h)
BL = attribute (PCjr only) or color (graphics mode)
if bit 7 set in graphics mode, character is xor'ed onto screen
CX = number of times to write character
Notes: all characters are displayed, including CR, LF, and BS
replication count in CX may produce an unpredictable result in graphics
modes if it is greater than the number of positions remaining in the
current row
----------100B--BH00-------------------------
INT 10 - VIDEO - SET BACKGROUND/BORDER COLOR
AH = 0Bh
BH = 00h
BL = background/border color (border only in text modes)
----------100B--BH01-------------------------
INT 10 - VIDEO - SET PALETTE
AH = 0BH
BH = 01h
BL = palette ID
00h background, green, red, and brown/yellow
01h background, cyan, magenta, and white
----------100C-------------------------------
INT 10 - VIDEO - WRITE GRAPHICS PIXEL
AH = 0Ch
BH = page number
AL = pixel color (if bit 7 set, value is xor'ed onto screen)
CX = column
DX = row
Notes: valid only in graphics modes
BH is ignored if the current video mode supports only one page
----------100D-------------------------------
INT 10 - VIDEO - READ GRAPHICS PIXEL
AH = 0Dh
BH = page number
CX = column
DX = row
Return: AL = pixel color
Notes: valid only in graphics modes
BH is ignored if the current video mode supports only one page
----------100E-------------------------------
INT 10 - VIDEO - TELETYPE OUTPUT
AH = 0Eh
AL = character to write
BH = page number
BL = foreground color (graphics modes only)
Notes: characters 07h (BEL), 08h (BS), 0Ah (LF), and 0Dh (CR) are interpreted
and do the expected things
IBM PC ROMs dated 4/24/81 and 10/19/81 require that BH be the same as
the current active page
----------100F-------------------------------
INT 10 - VIDEO - GET CURRENT VIDEO MODE
AH = 0Fh
Return: AH = number of character columns
AL = display mode (see AH=00h)
BH = active page (see AH=05h)
Notes: if mode was set with bit 7 set ("no blanking"), the returned mode will
also have bit 7 set
EGA and VGA return either AL=03h (color) or AL=07h (monochrome) in all
extended-row text modes
----------101000----------------------------
INT 10 - VIDEO - SET SINGLE PALETTE REGISTER (PCjr,EGA,MCGA,VGA)
AX = 1000h
BL = palette register number (00h-0Fh)
= attribute register number (undocumented)
10h attribute mode control register (should let BIOS control
this)
11h overscan color register (see also AX=1001h)
12h color plane enable register (bits 3-0 enable corresponding
text attribute bit)
13h horizontal PEL panning register
14h color select register
BH = color or attribute register value
Notes: on MCGA, only BX = 0712h is supported
----------101001-----------------------------
INT 10 - VIDEO - SET BORDER (OVERSCAN) COLOR (PCjr,EGA,VGA)
AX = 1001h
BH = border color (00h-3Fh)
BUG: the original IBM VGA BIOS incorrectly updates the parameter save area
and places the border color at offset 11h of the palette table
rather than offset 10h
----------101002-----------------------------
INT 10 - VIDEO - SET ALL PALETTE REGISTERS (PCjr,EGA,VGA)
AX = 1002h
ES:DX -> palette register list
Format of palette register list:
Offset Size Description
00h 16 BYTEs colors for palette registers 00h through 0Fh
10h BYTE border color
----------101003-----------------------------
INT 10 - VIDEO - TOGGLE INTENSITY/BLINKING BIT (Jr, PS, TANDY 1000, EGA, VGA)
AX = 1003h
BL = new state
00h background intensity enabled
01h blink enabled
Note: although there is no function to get the current status, bit 5 of
0040h:0065h indicates the state
----------101007-----------------------------
INT 10 - VIDEO - GET INDIVIDUAL PALETTE REGISTER (VGA)
AX = 1007h
BL = palette or attribute (undoc) register number (see AX=1000h)
Return: BH = palette or attribute register value
----------101008-----------------------------
INT 10 - VIDEO - READ OVERSCAN (BORDER COLOR) REGISTER (VGA)
AX = 1008h
Return: BH = border color (00h-3Fh)
----------101009-----------------------------
INT 10 - VIDEO - READ ALL PALETTE REGISTERS AND OVERSCAN REGISTER (VGA)
AX = 1009h
ES:DX -> 17-byte buffer (see AX=1002h)
----------101010-----------------------------
INT 10 - VIDEO - SET INDIVIDUAL DAC REGISTER (VGA/MCGA)
AX = 1010h
BX = register number
CH = new value for green (0-63)
CL = new value for blue (0-63)
DH = new value for red (0-63)
----------101012-----------------------------
INT 10 - VIDEO - SET BLOCK OF DAC REGISTERS (VGA/MCGA)
AX = 1012h
BX = starting color register
CX = number of registers to set
ES:DX -> table of 3*CX bytes where each 3 byte group represents one
byte each of red, green and blue (0-63)
----------101013-----------------------------
INT 10 - VIDEO - SELECT VIDEO DAC COLOR PAGE (VGA)
AX = 1013h
BL = subfunction
00h select paging mode
BH = 00h select 4 blocks of 64
BH = 01h select 16 blocks of 16
01h select page
BH = page number (00h to 03h) or (00h to 0Fh)
Note: not valid in mode 13h
----------101015-----------------------------
INT 10 - VIDEO - READ INDIVIDUAL DAC REGISTER (VGA/MCGA)
AX = 1015h
BL = palette register number
Return: DH = red value
CH = green value
CL = blue value
----------101017-----------------------------
INT 10 - VIDEO - READ BLOCK OF DAC REGISTERS (VGA/MCGA)
AX = 1017h
BX = starting palette register
CX = number of palette registers to read
ES:DX -> buffer (3 * CX bytes in size) (see also AX=1012h)
Return: buffer filled with CX red, green and blue triples
----------101018-----------------------------
INT 10 - VIDEO - undocumented - SET PEL MASK (VGA/MCGA)
AX = 1018h
BL = new PEL value
----------101019-----------------------------
INT 10 - VIDEO - undocumented - READ PEL MASK (VGA/MCGA)
AX = 1019h
Return: BL = value read
----------10101A-----------------------------
INT 10 - VIDEO - GET VIDEO DAC COLOR-PAGE STATE (VGA)
AX = 101Ah
Return: BL = paging mode
00h four pages of 64
01h sixteen pages of 16
BH = current page
----------10101B-----------------------------
INT 10 - VIDEO - PERFORM GRAY-SCALE SUMMING (VGA/MCGA)
AX = 101Bh
BX = starting palette register
CX = number of registers to convert
----------1011-------------------------------
INT 10 - VIDEO - TEXT-MODE CHARACTER GENERATOR FUNCTIONS (PS, EGA, VGA)
AH = 11h
The following functions will cause a mode set, completely resetting
the video environment, but without clearing the video buffer
AL = 00h, 10h: load user-specified patterns
ES:BP -> user table
CX = count of patterns to store
DX = character offset into map 2 block
BL = block to load in map 2
BH = number of bytes per character pattern
AL = 01h, 11h: load ROM monochrome patterns (8 by 14)
BL = block to load
AL = 02h, 12h: load ROM 8 by 8 double-dot patterns
BL = block to load
AL = 03h: set block specifier
BL = block specifier
(EGA/MCGA) bits 0,1 = block selected by chars with attribute
bit 3=0
bits 2,3 = block selected by chars with attribute
bit 3=1
(VGA) bits 0,1,4 = block selected by attribute bit 3 = 0
bits 2,3,5 = block selected by attribute bit 3 = 1
AL = 04h, 14h: load ROM 8x16 character set (VGA)
BL = block to load
The routines called with AL=1xh are designed to be called only immediately
after a mode set and are similar to the routines called with AL=0xh,
except that:
Page 0 must be active.
Bytes/character is recalculated.
Max character rows is recalculated.
CRT buffer length is recalculated.
CRTC registers are reprogrammed as follows:
R09 = bytes/char-1 ; max scan line (mode 7 only)
R0A = bytes/char-2 ; cursor start
R0B = 0 ; cursor end
R12 = ((rows+1)*(bytes/char))-1 ; vertical display end
R14 = bytes/char; underline loc
(*** BUG: should be 1 less ***)
----------1011-------------------------------
INT 10 - VIDEO - GRAPHICS-MODE CHARACTER GENERATOR FUNCTIONS (PS, EGA, VGA)
AH = 11h
AL = 20h: set user 8 by 8 graphics characters (INT 1F)
ES:BP -> user table
AL = 21h: set user graphics characters
ES:BP -> user table
CX = bytes per character
BL = row specifier
00h user set
DL = number of rows
01h 14 rows
02h 25 rows
03h 43 rows
AL = 22h: ROM 8 by 14 set
BL = row specifier (see above)
AL = 23h: ROM 8 by 8 double dot
BL = row specifier (see above)
AL = 24h: load 8x16 graphics characters (VGA/MCGA)
BL = row specifier (see above)
AL = 29h: load 8x16 graphics characters (Compaq Systempro)
BL = row specifier (see above)
Notes: these functions are meant to be called only after a mode set
----------101130-----------------------------
INT 10 - VIDEO - GET FONT INFORMATION (EGA, MCGA, VGA)
AX = 1130h
BH = pointer specifier
00h INT 1Fh pointer
01h INT 43h pointer
02h ROM 8x14 character font pointer
03h ROM 8x8 double dot font pointer
04h ROM 8x8 double dot font (high 128 characters)
05h ROM alpha alternate (9 by 14) pointer (EGA,VGA)
06h ROM 8x16 font (MCGA, VGA)
07h ROM alternate 9x16 font (VGA only)
Return: ES:BP = specified pointer
CX = bytes/character
DL = character rows on screen - 1
----------1012--BL10-------------------------
INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (PS, EGA, VGA, MCGA) - GET EGA INFO
AH = 12h
BL = 10h
Return: BH = 00h color mode in effect (I/O port 3Dxh)
01h mono mode in effect (I/O port 3Bxh)
BL = 00h 64k bytes memory installed
01h 128k bytes memory installed
02h 192k bytes memory installed
03h 256k bytes memory installed
CH = feature bits
CL = switch settings
----------1012--BL20-------------------------
INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (PS,EGA,VGA,MCGA) - ALTERNATE PRTSC
AH = 12h
BL = 20h select alternate print screen routine
Notes: installs a PrtSc routine from the video card's BIOS to replace the
default PrtSc handler from the ROM BIOS, which usually does not
understand screen heights other than 25 lines
some adapters disable print-screen instead of enhancing it
----------1012--BL30-------------------------
INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (VGA) - SELECT VERTICAL RESOLUTION
AH = 12h
BL = 30h
AL = vertical resolution
00h 200 scan lines
01h 350 scan lines
02h 400 scan lines
Return: AL = 12h if function supported
----------1012--BL31-------------------------
INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (VGA, MCGA) - PALETTE LOADING
AH = 12h
BL = 31h
AL = 00h enable default palette loading
01h disable default palette loading
Return: AL = 12h if function supported
----------1012--BL32-------------------------
INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (VGA, MCGA) - VIDEO ADDRESSING
AH = 12h
BL = 32h
AL = 00h enable video addressing
01h disable video addressing
Return: AL = 12h if function supported
Desc: Specifies whether the CPU should have access to video memory and the
display adapter's I/O registers
----------1012--BL33-------------------------
INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (VGA, MCGA) - GRAY-SCALE SUMMING
AH = 12h
BL = 33h
AL = 00h enable grey scale summing
01h disable grey scale summing
Return: AL = 12h if function supported
----------1012--BL34-------------------------
INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (VGA) - CURSOR EMULATION
AH = 12h
BL = 34h
AL = 00h enable alphanumeric cursor emulation
01h disable alphanumeric cursor emulation
Return: AL = 12h if function supported
----------1012--BL35-------------------------
INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (PS) - DISPLAY-SWITCH INTERFACE
AH = 12h
BL = 35h
AL = 00h initial adapter video off
01h initial planar video on
02h switch active video off
03h switch inactive video on
80h *UNDOCUMENTED* set system board video active flag
ES:DX -> buffer (128 byte save area if AL = 0, 2 or 3)
Return: AL = 12h if function supported
----------1012--BL36-------------------------
INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (PS, VGA) - VIDEO REFRESH CONTROL
AH = 12h
BL = 36h
AL = 00h enable refresh
01h disable refresh
Return: AL = 12h if function supported
----------1013-------------------------------
INT 10 - VIDEO - WRITE STRING (AT and later,EGA)
AH = 13h
AL = write mode
bit 0: update cursor after writing
1: string contains alternating characters and attributes
BH = page number
BL = attribute if string contains only characters
CX = number of characters in string
DH,DL = row,column at which to start writing
ES:BP -> string to write
Notes: recognises CR, LF, BS, and bell
also available PC or XT with EGA or higher
HP 95LX only supports write mode 00h
BUG: on the IBM VGA Adapter, any scrolling which may occur is performed on
the active page rather than the requested page
----------101A-------------------------------
INT 10 - VIDEO - DISPLAY COMBINATION (PS,VGA/MCGA)
AH = 1Ah
AL = 00h read display combination code
Return: BL = active display code (see below)
BH = alternate display code
01h set display combination code
BL = active display code (see below)
BH = alternate display code
Return: AL = 1Ah if function was supported
Values for display combination code:
00h no display
01h monochrome adapter w/ monochrome display
02h CGA w/ color display
03h reserved
04h EGA w/ color display
05h EGA w/ monochrome display
06h PGA w/ color display
07h VGA w/ monochrome analog display
08h VGA w/ color analog display
09h reserved
0Ah MCGA w/ digital color display
0Bh MCGA w/ monochrome analog display
0Ch MCGA w/ color analog display
FFh unknown display type
----------101B-------------------------------
INT 10 - VIDEO - FUNCTIONALITY/STATE INFORMATION (PS,VGA/MCGA)
AH = 1Bh
BX = implementation type
0000h return functionality/state information
ES:DI -> 64 byte buffer for state information (see below)
Return: AL = 1Bh if function supported
ES:DI buffer filled with state information
Format of state information:
Offset Size Description
00h DWORD address of static functionality table (see below)
04h BYTE video mode in effect
05h WORD number of columns
07h WORD length of regen buffer in bytes
09h WORD starting address of regen buffer
0Bh WORD cursor position for page 0
0Dh WORD cursor position for page 1
0Fh WORD cursor position for page 2
11h WORD cursor position for page 3
13h WORD cursor position for page 4
15h WORD cursor position for page 5
17h WORD cursor position for page 6
19h WORD cursor position for page 7
1Bh WORD cursor type
1Dh BYTE active display page
1Eh WORD CRTC port address
20h BYTE current setting of register (3?8)
21h BYTE current setting of register (3?9)
22h BYTE number of rows
23h WORD bytes/character
25h BYTE display combination code of active display
26h BYTE DCC of alternate display
27h WORD number of colors supported in current mode
29h BYTE number of pages supported in current mode
2Ah BYTE number of scan lines active
(0,1,2,3) = (200,350,400,480)
2Bh BYTE primary character block
2Ch BYTE secondary character block
2Dh BYTE miscellaneous flags
bit 0 all modes on all displays on
1 grey summing on
2 monochrome display attached
3 default palette loading disabled
4 cursor emulation enabled
5 0 = intensity; 1 = blinking
6 PS/2 P70 plasma display (without 9-dot wide font) active
7 reserved
2Eh 3 BYTEs reserved (00h)
31h BYTE video memory available
00h = 64K, 01h = 128K, 02h = 192K, 03h = 256K
32h BYTE save pointer state flags
bit 0 512 character set active
1 dynamic save area present
2 alpha font override active
3 graphics font override active
4 palette override active
5 DCC override active
6 reserved
7 reserved
33h 13 BYTEs reserved (00h)
Format of Static Functionality Table:
Offset Size Description
00h BYTE modes supported #1
bit 0 to bit 7 = 1 modes 0,1,2,3,4,5,6 supported
01h BYTE modes supported #2
bit 0 to bit 7 = 1 modes 8,9,0Ah,0Bh,0Ch,0Dh,0Eh,0Fh supported
02h BYTE modes supported #3
bit 0 to bit 3 = 1 modes 10h,11h,12h,13h supported
bit 4 to bit 7 reserved
03h 4 BYTEs reserved
07h BYTE scan lines supported
bit 0 to bit 2 = 1 if scan lines 200,350,400 supported
08h BYTE total number of character blocks available in text modes
09h BYTE maximum number of active character blocks in text modes
0Ah BYTE miscellaneous function flags #1
bit 0 all modes on all displays function supported
1 grey summing function supported
2 character font loading function supported
3 default palette loading enable/disable supported
4 cursor emulation function supported
5 EGA palette present
6 color palette present
7 color paging function supported
0Bh BYTE miscellaneous function flags #2
bit 0 light pen supported
1 save/restore state function 1Ch supported
2 intensity blinking function supported
3 Display Combination Code supported
4-7 reserved
0Ch WORD reserved
0Eh BYTE save pointer function flags
bit 0 512 character set supported
1 dynamic save area supported
2 alpha font override supported
3 graphics font override supported
4 palette override supported
5 DCC extension supported
6 reserved
7 reserved
0Fh BYTE reserved
----------101C-------------------------------
INT 10 - VIDEO - SAVE/RESTORE VIDEO STATE (PS50+,VGA)
AH = 1Ch
AL = 00h return state buffer size
Return: BX = number of 64-byte blocks needed
01h save video state
ES:BX -> buffer
02h restore video state
ES:BX -> buffer containing previously saved state
CX = requested states
bit 0 video hardware
1 BIOS data areas
2 color registers and DAC state
3-15 reserved
Return: AL = 1Ch if function supported
Format of video hardware state:
Offset Size Description
00h BYTE sequencer index register
01h BYTE CRTC index register
02h BYTE graphics controller index register
03h BYTE attribute controller index register
04h BYTE feature controller register
05h 4 BYTEs sequencer registers
09h BYTE sequencer register 0
0Ah 25 BYTEs CRTC registers 0-8
23h 16 BYTEs palette registers 00h-0Fh
33h 4 BYTEs attribute registers 10h-13h
37h 9 BYTEs graphics controller registers 0-8
40h BYTE CRTC base address (low)
41h BYTE CRTC base address (high)
42h BYTE plane 0 latch
43h BYTE plane 1 latch
44h BYTE plane 2 latch
45h BYTE plane 3 latch
Format of DAC state:
Offset Size Description
00h BYTE read/write mode DAC
01h BYTE pixel address
02h BYTE pixel mask
03h 768 BYTEs color data (256 triples)
303h BYTE color select register
Memory:
0:410h WORD Bit 4-5: Initial video mode
0: EGA,VGA,PGA 1:40x25 color, 2: 80x25 color,
3: 80x25 monochrome
0:449h BYTE Video current mode
0:44Ah WORD Video columns on screen
0:44Ch WORD Video page (regen buffer) size in bytes
0:44Eh WORD Video current page start address in regen buffer
0:450h 16 BYTEs Video cursor position (col, row) for eight pages, 0 based
0:460h WORD Video cursor type, 6845 compatible, hi=startline, lo=endline
0:462h BYTE Video current page number
0:463h WORD Video CRT controller base address: color=03D4h, mono=03B4h
0:465h BYTE Video current setting of mode select register 03D8h/03B8h
0:466h BYTE Video current setting of CGA palette register 03D9h
0:484h BYTE Video EGA/MCGA/VGA rows on screen minus one
0:485h WORD Video EGA/MCGA/VGA character height in scan-lines
0:487h BYTE Video EGA/VGA control: [MCGA: =00h]
bit 0: =0 alphanumeric cursor emulation enabled, =1 not.
When enabled the text mode cursor size (INT 10h,
AH=01h) are translated to EGA/VGA size.
1: =0 for color or ECD monitor, =1 for mono monitor
2: =1 if to wait for display enable (what means this?)
3: =0 if EGA/VGA video system active, =1 if inactive
4: reserved
6-5: RAM on adapter = (this field + 1) * 64K
7: =1 if not to clear RAM (see INT 10h, AH=00h)
0:488h BYTE Video EGA/VGA switches: [MCGA: reserved]
bits 0-3: configuration switches 4-1 (=0 on, =1 off)
Values as read:
0h Pri MDA, Sec EGA+old color display 40 x 25
1h Pri MDA, Sec EGA+old color display 80 x 25
2h Pri MDA, Sec EGA+ECD normal mode (CGA
emulation)
3h Pri MDA, Sec EGA+ECD enhanced mode
4h Pri CGA 40 x 25, Sec EGA mono display
5h Pri CGA 80 x 25, Sec EGA mono display
6h Pri EGA+old color display 40 x 25, Sec MDA
7h Pri EGA+old color display 80 x 25, Sec MDA
8h Pri EGA+ECD normal mode (CGA emul), Sec MDA
9h Pri EGA+ECD enhanced mode, Sec MDA
Ah Pri EGA mono display, Sec CGA 40 x 25
Bh Pri EGA mono display, Sec CGA 80 x 25
bits 7-4: power-on state of feature connector bits 3-0
Note: When bit4 of 40h:89h is 0, VGA emulates 350-line EGA if
this byte is x3h or x9h, otherwise emulates 200-line CGA in
400-line double scan. VGA resets this byte to x9h after the
mode set.
0:489h BYTE Video MCGA/VGA mode-set option control:
bit 0: [VGA] =1 if VGA active, =0 if not
[MCGA] reserved, zero
1: =1 if grey scale summing enabled, =0 if disabled
2: =1 if mono display, =0 if color display
3: =0 if default palette loading enabled at mode set
4: [VGA] =1 if to use 400-line mode at next mode set
=0 if to emulate EGA at next mode set
This bit set to 1 after the mode set.
[MCGA] =1 use 400-line mode at next mode set
=0 emulate CGA, digital monitor, 200 lines,
8 x 8 text font at next mode set
Bit unchanged by mode set.
5: reserved
6: =1 if display switching enabled, =0 if disabled
bits 7 and 4:
0 0 350-line mode requested
0 1 400-line mode at next mode set
1 0 200-line mode requested
1 1 reserved
Note: Apparently VGA BIOS mode set disregards bit 7 and uses
byte 40h:88h to determine 200/350 selection when bit 4
is zero . Presumably bit 7 is a convenience for other
purposes. Bit 7 is reset to zero after the mode set.
0:48Ah BYTE Video [MCGA/VGA]: index into Display Combination Code table
0:4A8h DWORD Pointer to the Video Save Pointer Table (see below)
Format of Video Save Pointer Table [EGA/VGA/MCGA only]:
Offset Size Description
00h DWORD ptr to Video Parameter Table
04h DWORD ptr to Parameter Dynamic Save Area, else 0 [EGA/VGA only]
08h DWORD ptr to Alphanumeric Character Set Override, else 0
0Ch DWORD ptr to Graphics Character Set Override, else 0
10h DWORD [VGA only] ptr to Secondary Save Pointer Table, must be valid
14h DWORD reserved, zero
18h DWORD reserved, zero
Note: table initially in ROM, copy to RAM to alter, then update 40h:A8h.
Format of Secondary Video Save Pointer Table [VGA only]:
Offset Size Description
00h WORD Length of this table in bytes, including this word (1Ah)
02h DWORD ptr to Display Combination Code Table, must be valid
06h DWORD ptr to second Alphanumeric Character Set Override, else 0
0Ah DWORD ptr to User Palette Profile Table, else 0
0Eh DWORD reserved, zero
12h DWORD reserved, zero
16h DWORD reserved, zero
Note: table initially in ROM, copy to RAM to alter, then alter Save Ptr Table.
Format of Video Parameter Table [EGA, VGA only]:
An array of 23 [EGA] or 29 [VGA] elements, each element being 64 bytes long.
Elements appear in the order:
00h-03h Modes 00h-03h in 200-line CGA emulation mode
04h-0Eh Modes 04h-0Eh
0Fh-10h Modes 0Fh-10h when only 64kB RAM on adapter
11h-12h Modes 0Fh-10h when >64kB RAM on adapter
13h-16h Modes 00h-03h in 350-line mode
17h VGA Modes 00h or 01h in 400-line mode
18h VGA Modes 02h or 03h in 400-line mode
19h VGA Mode 07h in 400-line mode
1Ah-1Ch VGA Modes 11h-13h
Format of Video Parameter Table element [EGA, VGA only]:
Offset Size Description
00h BYTE Columns on screen (see 0:44Ah)
01h BYTE Rows on screen minus one (see 0:484h)
02h BYTE Height of character in scan lines (see 0:485h)
03h WORD Size of video buffer (see 0:44Ch)
05h 4 BYTEs Values for Sequencer Registers 1-4
09h BYTE Value for Miscellaneous Output Register
0Ah 25 BYTEs Values for CRTC Registers 00h-18h
23h 20 BYTEs Values for Attribute Controller Registers 00h-13h
37h 9 BYTEs Values for Graphics Controller Registers 00h-08h
Format of Video Parameter Table [MCGA only] {guesswork from inspection}:
16 triplet BYTEs of R,G,B DAC info for 16 colors;
An array of 11 elements, each element being 32 bytes long.
Elements appear in the order:
Modes 00h,01h in 200-line mode for digital displays
Modes 00h,01h in 400-line mode for analog displays
Modes 02h,03h in 200-line mode for digital displays
Modes 02h,03h in 400-line mode for analog displays
Modes 04h,05h in 200-line mode for digital displays
Modes 04h,05h in 400-line mode for analog displays
Mode 06h in 200-line mode for digital displays
Mode 06h in 400-line mode for analog displays
Mode 11h
Mode 13h in 200-line mode for digital displays
Mode 13h in 400-line mode for analog displays
Format of Video Parameter Table element [MCGA only]:
Offset Size Description
00h BYTE Columns on screen (see 0:44Ah)
01h BYTE Rows on screen minus one (see 0:484h)
02h BYTE Height of character in scan lines (see 0:485h)
03h WORD Size of video buffer (see 0:44Ch)
05h WORD ??? always zero
07h 21 BYTEs Video data registers 00h-14h to port 3D5h indexed by 3D4h
1Ch BYTE PEL Mask to port 3C6h
1Dh BYTE CGA Mode Control to port 3D8h
1Eh BYTE CGA Border Control to port 3D9h
1Fh BYTE Extended Mode Control to port 3DDh
Format of Video Parameter Dynamic Save Area [EGA, VGA only]:
Offset Size Description
00h 16 BYTEs Last data written to Attribute Contr. Palette Registers 0-15
10h BYTE Last data written to Attribute Controller Overscan Register
11h-FFh Reserved
Note: Need for table was that EGA registers were write-only.
Note: If default values (from the Video Parameter Table) are
over-ridden at a mode set by the VGA User Palette Profile
Table, then the Dynamic Save Area is updated with the
default values, not the User Profile ones.