Assembly Language Help (alang.hlp) (Table of Contents; Topic list)
Int 10h Function 12h Subfunction 35h
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  Interrupt:   10h     Function:   12h     Subfunction:   35h
 
  Title:       Switch Active Display
 
  Description:                                              [MCGA] [VGA]
 
     Allows selection of one of two video adapters in the system, when
     memory use or port addresses conflict between the two adapters.
 
     Input                                 Output
 
     AH = 12h                              If function supported
     AL = Switching function                 AL = 12h
        = 00h to disable initial           And if called with AL = 00h
          video adapter                    or 02h
        = 01h to enable system board         Video adapter state information
          video adapter                      saved in caller's buffer
        = 02h to disable active            Or if called with AL = 03h
          video adapter                      Video adapter state restored
        = 03h to enable inactive             from information in caller's
          video adapter                      buffer
     BL = 35h
     ES:DX = segment:offset of 128-byte
             buffer (if AL = 00h,
             02h, or 03h)
                                    -♦-