EGA Switch Settings

 This topic discusses the switches on older IBM-logoed EGA cards ONLY.
 On non-IBM EGA cards, there may be more or fewer switches and they may
 have different meanings.

 The DIP switches on the rear of the EGA indicate which display monitor
 is connected to the card and which (if any) other adapters are in the
 system at the same time.  The switches are mirrored in memory.  See
 EGA Data Areas.

 There is one CRITICAL thing to watch for:  never plug a Monochrome monitor
 into the EGA adapter unless the switches are set to accept it.  A wrong
 setting will actually do physical damage to the monitor!

 In the following table, Primary indicates the adapter/monitor which is
 first enabled when the computer is turned on.  Secondary indicates an
 optional second adapter/monitor which may be connected.

ON Ö4Â3Â2Â1· Primary EGA connected to 40x25 color monitor
 ^ ºß³Ü³Ü³ßº Secondary MDA
   ÓÄÁÄÁÄÁĽ
ON Ö4Â3Â2Â1· Primary EGA connected to 80x25 color monitor
 ^ ºß³Ü³Ü³Üº Secondary MDA
   ÓÄÁÄÁÄÁĽ
ON Ö4Â3Â2Â1· Primary EGA connected to enhanced color monitor (CGA emulation)
 ^ ºÜ³ß³ß³ßº Secondary MDA
   ÓÄÁÄÁÄÁĽ
ON Ö4Â3Â2Â1· Primary EGA connected to enh. color monitor (best resolution)
 ^ ºÜ³ß³ß³Üº Secondary MDA
   ÓÄÁÄÁÄÁĽ
ON Ö4Â3Â2Â1· Primary EGA connected to Monochrome monitor
 ^ ºÜ³ß³Ü³ßº Secondary CGA connected to 40x25 color monitor
   ÓÄÁÄÁÄÁĽ
ON Ö4Â3Â2Â1· Primary EGA connected to Monochrome monitor
 ^ ºÜ³ß³Ü³Üº Secondary CGA connected to 80x25 color monitor
   ÓÄÁÄÁÄÁĽ

ON Ö4Â3Â2Â1· Primary MDA
 ^ ºß³ß³ß³ßº Secondary EGA connected to 40x25 color monitor
   ÓÄÁÄÁÄÁĽ
ON Ö4Â3Â2Â1· Primary MDA
 ^ ºß³ß³ß³Üº Secondary EGA connected to 80x25 color monitor
   ÓÄÁÄÁÄÁĽ
ON Ö4Â3Â2Â1· Primary MDA
 ^ ºß³ß³Ü³ßº Secondary EGA connected to enh. color monitor (CGA emulation)
   ÓÄÁÄÁÄÁĽ
ON Ö4Â3Â2Â1· Primary MDA
 ^ ºß³ß³Ü³Üº Secondary EGA connected to enh. monitor (best resolution)
   ÓÄÁÄÁÄÁĽ
ON Ö4Â3Â2Â1· Primary CGA connected to 40x25 color monitor
 ^ ºß³Ü³ß³ßº Secondary EGA connected to Monochrome monitor
   ÓÄÁÄÁÄÁĽ
ON Ö4Â3Â2Â1· Primary CGA connected to 80x25 color monitor
 ^ ºß³Ü³ß³Üº Secondary EGA connected to Monochrome monitor
   ÓÄÁÄÁÄÁĽ

ÛÝEGA JumpersÞÛ
  The three jumpers on the EGA control various features of the card.  The
  jumper/connectors are used as follows:
    ÉP1Í»
  1 ºÚo¿º Supports enhanced color monitor
  2 ºÀoÙº (640x350 and 64 color capability)
  3 º o º
    ÈÍÍͼ
    ÉP1Í»
  1 º o º
  2 ºÚo¿º Supports color monitor only
  3 ºÀoÙº (640x200 and 16 color capability)
    ÈÍÍͼ

    P2 (not shown) is a connector for a light pen.

    ÉP3Í»
  1 ºÚo¿º Sets EGA I/O ports to 3xxH
  2 ºÀoÙº (normal setting)
  3 º o º
    ÈÍÍͼ
    ÉP3Í»
  1 º o º
  2 ºÚo¿º Sets EGA I/O ports to 2xxH
  3 ºÀoÙº NOT supported by EGA BIOS
    ÈÍÍͼ

See Also: Equipment List
          EGA Data Areas
          Switch Settings
          EGA Video Adaptor Pin Outs
                                    -*-