VGA timing information
This documents tries to collect together information about standard VGA card timing details.
Information form HP monitor manual
Horizonal Timing
Horizonal Dots 640 640 640 Vertical Scan Lines 350 400 480 Horiz. Sync Polarity POS NEG NEG A (us) 31.77 31.77 31.77 Scanline time B (us) 3.77 3.77 3.77 Sync pulse lenght C (us) 1.89 1.89 1.89 Back porch D (us) 25.17 25.17 25.17 Active video time E (us) 0.94 0.94 0.94 Front porch
______________________ ________
________| VIDEO |________| VIDEO (next line)
|-C-|----------D-----------|-E-|
__ ______________________________ ___________
|_| |_|
|B|
|---------------A----------------|
Vertical Timing
Horizonal Dots 640 640 640 Vertical Scan Lines 350 400 480 Vert. Sync Polarity NEG POS NEG Vertical Frequency 70Hz 70Hz 60Hz O (ms) 14.27 14.27 16.68 Total frame time P (ms) 0.06 0.06 0.06 Sync length Q (ms) 1.88 1.08 1.02 Back porch R (ms) 11.13 12.72 15.25 Active video time S (ms) 1.2 0.41 0.35 Front porch
______________________ ________
________| VIDEO |________| VIDEO (next frame)
|-Q-|----------R-----------|-S-|
__ ______________________________ ___________
|_| |_|
|P|
|---------------O----------------|
Informations source
- HP D1194A Super VGA Display & HP D1195A Erognomic Super VGA Display Installation Guide, Hewlett Packard
"VGA industry standard" 640x480 pixel mode
General characteristics
Clock frequency 25.175 MHz Line frequency 31469 Hz Field frequency 59.94 Hz
One line
8 pixels front porch 96 pixels horizontal sync 40 pixels back porch 8 pixels left border 640 pixels video 8 pixels right border --- 800 pixels total per line
One field
2 lines front porch 2 lines vertical sync 25 lines back porch 8 lines top border 480 lines video 8 lines bottom border --- 525 lines total per field
Other details
Sync polarity: H negative, V negative Scan type: non interlaced.
Information source
- Article "Re: VGA specifications ,where ?" posted 19 Nov 1997 to sci.electronics.design newsgroup by Jeroen Stessen
More VGA mode information
There are the 3 "standard" VGA modes that each VGA card is supposed to be able to do:
- 640 x 350 x 70 is compatible with the old EGA mode, but on a VGA display.
- 640 x 400 x 70 is the MS-DOS text mode (when the computer is booting !).
- 640 x 480 x 60 is the default Windows(tm) graphics mode (16 colours !).
Their line frequency is exactly twice that of the NTSC television system, or almost twice that of the PAL television system. This makes it fairly easy to implement a VGA input on a television set that uses line doubling for the television signals so the line deflection already runs on 31 kHz.
The following timings come from a list of 82 different computer timings, and by now there will be even more. Some video cards even have variable timing (allowing the user to set width, height and shift...). The only standard is that there is no standard !
"640 x 350 (EGA on VGA)" "640 x 400 VGA text" "VGA industry standard" Clock frequency 25.175 MHz Clock frequency 25.175 MHz Clock frequency 25.175 MHz Line frequency 31469 Hz Line frequency 31469 Hz Line frequency 31469 Hz Field frequency 70.086 Hz Field frequency 70.086 Hz Field frequency 59.94 Hz One line: One line: One line: 8 pixels front porch 8 pixels front porch 8 pixels front porch 96 pixels horizontal sync 96 pixels horizontal sync 96 pixels horizontal sync 40 pixels back porch 40 pixels back porch 40 pixels back porch 8 pixels left border 8 pixels left border 8 pixels left border 640 pixels video 640 pixels video 640 pixels video 8 pixels right border 8 pixels right border 8 pixels right border --- --- --- 800 pixels total per line 800 pixels total per line 800 pixels total per line
One field: One field: One field: 31 lines front porch 5 lines front porch 2 lines front porch 2 lines vertical sync 2 lines vertical sync 2 lines vertical sync 54 lines back porch 28 lines back porch 25 lines back porch 6 lines top border 7 lines top border 8 lines top border 350 lines video 400 lines video 480 lines video 6 lines bottom border 7 lines bottom border 8 lines bottom border --- --- --- 449 lines total per field 449 lines total per field 525 lines total per field
Sync polarity: H positive, Sync polarity: H negative, Sync polarity: H negative,
V negative V positive V negative
Scan type: non interlaced. Scan type: non interlaced. Scan type: non interlaced.
Information source
Jeroen H. Stessen kindly mailed this information for me to be added to this document at November 1997.
SuperVGA timing from NEC monitor manual
Horizontal :
______________ _____________
| | |
_______________| VIDEO |_______________| VIDEO (next line)
___________ _____________________ ______________________
|_| |_|
B C <------D-----><-E->
<----------A---------->
Vertical :
______________ _____________
| | |
_______________| VIDEO |_______________| VIDEO (next frame)
___________ _____________________ ______________________
|_| |_|
P Q <------R-----><-S->
<----------O---------->
For VESA 800*600 @ 60Hz:
Fh (kHz) :37.88 A (us) :26.4 B (us) :3.2 C (us) :2.2 D (us) :20.0 E (us) :1.0 Fv (Hz) :60.32 O (ms) :16.579 P (ms) :0.106 Q (ms) :0.607 R (ms) :15.84 S (ms) :0.026
Information source
- NEC Multisync manual
Necessary timing information about VGA modes
Vertical timing information
Mode name Lines line sync back active front whole frame
Total width pulse porch time porch period
(us) (us)(lin) (us)(lin) (us) (lin) (us)(lin) (us) (lin)
VGA 640x480 60Hz 525 31.78 63 2 953 30 15382 484 285 9 16683 525
VGA 640x480 72Hz 520 26.41 79 3 686 26 12782 484 184 7 13735 520
VGA 720x400 70Hz 449 31.78 63 2 1016 32 12839 404 349 11 14268 449
VGA 720x350 70Hz 449 31.78 63 2 1811 57 11250 354 1144 36 14268 449
VGA 800x600 56Hz 625 28.44 56 1 568 20 17177 604 -1* 17775 625
VGA 800x600 60Hz 628 26.40 106 4 554 21 15945 604 -1* 16579 628
VGA 800x600 72Hz 666 20.80 125 6 436 21 12563 604 728 35 13853 666
IBM 640x480 75Hz 525 25.397 51 2 761 30 12292 484 228 9 13333 525
MAC 640x480 66Hz 525 28.57 86 3 1057 37 13827 484 28 1 14999 525
Notes:
- Active area is actually an active area added with 4 overscan border lines (in some other VGA timing tables those border lines are included in back and front porch)
- Note than when the active part of VGA page is widened, it passes by the rising edge of the vertical sync signal in some modes (marked with *)
Horizonal timing information
Mode name Pixel sync back active front whole line
clock pulse porch time porch period
(MHz) (us) (pix) (pix) (pix) (pix) (pix)
VGA 640x480 60Hz 25.175 3.81 96 45 646 13 800
VGA 640x480 72Hz 31.5 1.27 40 125 646 21 832
VGA 720x400 70Hz 28.322 3.81 108 51 726 15 900
VGA 720x350 70Hz 28.322 3.81 108 51 726 15 900
VGA 800x600 56Hz 36 2 72 125 806 21 1024
VGA 800x600 60Hz 40 3.2 128 85 806 37 1056
VGA 800x600 72Hz 50 2.4 120 61 806 53 1040
IBM 640x480 75Hz 31.5 3.05 96 45 646 13 800
MAC 640x480 66Hz 30.24 2.11 64 93 646 61 864
Notes:
- Active area is actually an active area added with 6 overscan border pixels (in some other VGA timing tables those border pixels are included in back and front porch)
Information source
- Jere M�kel�, Software design for a video conversion equipment, Master's Thesis, Helsinki University of Technology,23. August 1994, Appendix B.1
Timing used in one VGA monitor tester product
The following timings are used in VTG-KIT VGA monitor tester kit sold my Data Sync Engineering.
Mode Horiz Vertical Horiz Vert Horiz HSYNC Vertical VSYNC
Dots Lines KHz Hz Sync Pol Sync Pol
VGA-480 640 480 31.5 60 3.8 us - 64 us -
VGA-400 640 400 31.5 70 3.8 us - 64 us +
SVGA I 800 600 35.2 56 2.0 us - 57 us -
SVGA II 800 600 37.8 60 3.2 us + 106 us +
SVGA III 800 600 48.0 72 2.4 us + 125 us +
XGA 1024 768 48.5 60 2.0 us - 124 us -
Information source:
Tomi Engdahl <[email protected]>