Option
/O[[VERLAYINTERRUPT]]:number
This option sets an interrupt number for passing control to overlays. By default, the interrupt number used for passing control to overlays is 63 (3F hexadecimal). The /OV option allows you to select a different interrupt number. This option is valid only when linking DOS programs.
The number can be any number from 0 to 255, specified in decimal format or in C-language notation. Numbers that conflict with DOS interrupts can be used; however, their use is not advised. You should use this option only when you want to use overlays with a program that already reserves interrupt 63 for some other purpose.