EGA DIP Switch Settings

SW1SW2SW3SW4Primary CardEGA Monitor TypeDIP Hex
0 (ON)0 (ON)0 (ON)0 (ON)MDA Primary + EGAColor (40x25)0
1 (OFF)0 (ON)0 (ON)0 (ON)MDA PrimaryColor (80x25)1
0 (ON)1 (OFF)0 (ON)0 (ON)MDA Primary + EGAEnhanced Color (in Normal Color Mode)2
1 (OFF)1 (OFF)0 (ON)0 (ON)MDA Primary + EGAEnhanced Color (in Enhanced Color Mode)3
0 (ON)0 (ON)1 (OFF)0 (ON)CGA Primary + EGAMonochrome (CGA Color (40x25))4
1 (OFF)0 (ON)1 (OFF)0 (ON)CGA Primary + EGAMonochrome (CGA Color (80x25))5
0 (ON)1 (OFF)1 (OFF)0 (ON)EGA Primary + MDAColor (40x25)6
1 (OFF)1 (OFF)1 (OFF)0 (ON)EGA Primary + MDAColor (80x25)7
0 (ON)0 (ON)0 (ON)1 (OFF)EGA Primary + MDAEnhanced Color (in Normal Color Mode)8
1 (OFF)0 (ON)0 (ON)1 (OFF)EGA Primary + MDAEnhanced Color (in Enhanced Color Mode)9
0 (ON)1 (OFF)0 (ON)1 (OFF)EGA Primary + CGAMonochrome (CGA Color (40x25))A
1 (OFF)1 (OFF)0 (ON)1 (OFF)EGA Primary + CGAMonochrome (CGA Color (80x25))B
0 (ON)0 (ON)1 (OFF)1 (OFF)reservedreservedreserved
1 (OFF)0 (ON)1 (OFF)1 (OFF)reservedreservedreserved
0 (ON)1 (OFF)1 (OFF)1 (OFF)reservedreservedreserved
1 (OFF)1 (OFF)1 (OFF)1 (OFF)reservedreservedreserved

Most EGA clone cards used the same settings - perhaps defining special interpretations of the last four unused settings on the original IBM EGA.

VGA cards or other cards without such DIP switches emulated the closest appropriate DIP HEX value to store in the BDA.

Note that DIP switches are read by the PC logically reversed. A switch that is ON reads logical low (0) while a switch that is OFF reads logically high (1).

Primary Emulation Resources