INT 61 - OPTIMA 1024 VGA-Sync,ET-3000 chipset - SET ZOOM WINDOW
        AX = 0006h
        BX:CX -> zoom window description (see below)
Notes:  width of zoom window must be a multiple of the pixel replication (zoom)
          factor
        INT 61 is the default interrupt; the actual interrupt number can be
          obtained by calling INT 16/AH=FFh
        not all vendors include the Tseng TSR which supports these functions
SeeAlso: AX=0000h"OPTIMA",AX=0001h"OPTIMA",AX=0005h"OPTIMA",AX=0008h"OPTIMA"
SeeAlso: INT 16/AH=FFh"OPTIMA"

Format of zoom window description:
Offset  Size    Description
 00h    WORD    X start of zoom window
 02h    WORD    Y start of zoom window
 04h    WORD    X end of zoom window
 06h    WORD    Y end of zoom window

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