The Software Pages - Mode Definition Parameters
Last updated on April 18th, 2001.

  • What's next:

      The following tables define the various parameters you need to configure or build a given mode for TV specifications.
      Any combination of horizontal and vertical definitions can be used, even if it doesn't make sense :-)
      If some of the data seems too technical, that's because it is. I will later give some application examples for Linux to illustrate. For other software, you need to find on that software a parameter with a name similar to what I give.

  • Abbreviations:

      HDE - Horizontal Display End
      SHB - Start Horizontal Blanking
      SHR - Start Horizontal Retrace
      EHR - End Horizontal Retrace
      EHB - End Horizontal Blanking
      HT - Horizontal Total

      VDE - Vertical Display End
      SVB - Start Vertical Blank
      VRS - Vertical Retrace Start
      VRE - Vertical Retrace End
      EVB - End Vertical Blank
      VT - Vertical Total

  • Definitions:

      Horizontal resolution:

      - All values are in pixels, except as noted;
      - 40 column text modes are 320 pixels, 8x8 character cell;
      - 80 column text modes have 640 pixels (8x8 character cell);
      - 132 column text modes are 1188 pixels wide (9x8 character cells);
      - SHB, SHR, EHR and EHB can be changed, provided the pixel differences between them remain constant. At minimum only SHR and EHR need to be changed in order to center the screen horizontally, however, the same restrictions apply;
      - Under no circumstance should SHR be able to be less than HDE;
      - A value greater than HT means it will be wrapped back to 0, so the actual value the one given less HT.
      - 'Standard' means only standard VGA clocks are used, 'Wide' uses a proprietary 7Mhz dot clock and 'Portrait' refers to portrait video mode formats, such as 768x1024.
      - Horizontal polarity is negative.

    Columns PAL NTSC Dot Clock (Mhz)
    HDE SHB SHR EHR EHB HT HDE SHB SHR EHR EHB HT
    320 Standard 320 504 528 584 656 808 320 472 520 576 632 800 12.587
    320 Wide 320 336 376 408 432 456 320 328 368 400 424 448 7.0805
    400 Standard 400 504 528 584 656 808 400 472 520 576 632 800 12.587
    400 Wide 376 376 400 432 464 456 368 368 392 424 536 448 7.0805
    512 512 616 656 720 792 904 512 600 656 720 776 896 14.161
    640 640 672 720 784 848 904 640 656 720 784 832 896 14.161
    720 720 672 760 824 848 904 720 656 752 816 832 896 14.161
    768 Portrait 768 1144 1192 1328 1488 1808 768 1128 1176 1312 1472 1792 28.322
    800 776 760 800 864 1072 904 776 752 800 864 1072 896 14.161
    960 960 1272 1320 1456 1616 1808 960 1272 1304 1440 1600 1792 28.322
    1024 1024 1272 1296 1432 1616 1808 1024 1256 1288 1424 1600 1792 28.322
    1024 16:9 1024 (1056) (1100) (1196) (1224) 1264 1024 (1056) (1100) (1196) (1216) 1248 19.750
    1188 1188 1260 1314 1431 1575 1611 1188 1242 1296 1413 1557 1593 25.175
    1152 1152 1328 1360 1496 672 1808 1152 1312 1352 1488 1656 1792 28.322
    1280 1280 1376 1424 1560 1720 1808 1280 1368 1416 1552 1712 1792 28.322
    1600 1568 1544 1592 1728 0 1808 1552 1528 1576 1712 1776 1792 28.322

      Vertical resolution:

      - All values are in lines;
      - For certain chipsets, interlaced mode is set as if the screen was not interlaced. This is called Frame Mode;
      - SVB, VRS, VRE and EVB can be changed, provided the line differences between them remain constant. At minimum only VRS and VRE need to be changed in order to center the screen vertically, however, the same restrictions apply;
      - Should the screen appear in black and white, try increasing or decreasing the VRE value by 1 (only);
      - Under no circumstance should VRS be able to be less than VDE;
      - Offset is CRTC register 13h and any extended bits available. Default value is as set by BIOS, except as noted. In addition, certain chipsets require this value to reflect the difference between 2 (instead of 1) adjacent lines, in interlaced mode. Because it is chipset dependent, I won't cover it here. You'll have to experiment. Wrong configuration will appear either as a crunched or an expanded screen;
      - Values in brackets need verification;
      - Vertical polarity is negative.

    Lines PAL NTSC Interlaced Offset
    VDE SVB VRS VRE EVB VT VDE SVB VRS VRE EVB VT
    350 175 231 234 238 256 313 175 204 207 211 225 263 Yes  
    192/384/768 192 239 242 246 264 313 192 215 218 222 236 263 No/Yes/Yes x1/x1/x2
    384/768 Frame 384 478 484 492 528 625 384 430 436 444 472 525 Yes x1/x2
    200/400 200 243 246 250 268 313 200 219 222 226 240 263 No/Yes  
    400 Frame 400 486 492 500 536 625 400 438 444 452 480 525 Yes  
    216/432/864 216 250 253 257 275 313 216 228 231 235 249 263 No/Yes/Yes x1/x1/x2
    240/480/960 240 263 266 270 288 313 240 239 242 246 260 263 No/Yes/Yes x1/x1/x2
    480/960 Frame 480 526 532 540 576 625 480 478 484 492 520 525 Yes x1/x2
    256/512/1024 256 271 274 278 296 313 249 247 250 254 7 263 No/Yes/Yes x1/x1/x2
    512/1024 Frame 512 542 548 556 592 625 498 494 500 508 14 525 Yes x1/x2
    540/1080 270 279 282 286 304 313 249 247 250 254 7 263 Yes x1/x2
    288/576/1152 288 288 291 295 2 313 260 258 261 265 18 263 No/Yes/Yes x1/x1/x2
    300/600/1200 295 293 296 300 7 313 260 258 261 265 18 263 No/Yes/Yes x1/x2
    600 Frame 590 586 592 600 13 625 520 516 522 5 36 525 Yes