INT 0cH: IRQ 4 COM1/3 / Stack Overflow

  INT 0cH is a hardware-generated interrupt (IRQ 4) forced by COM1 or COM3
  when it is done sending or receiving a byte of data.

█▌CPU Exception Interrupt▐█
  286+ computer execute INT 0cH when the CPU is in protected mode and it
  detects a stack access that is outside of the bounds of the SS selector.

  Protected-mode operating systems can watch for this and increase the size
  of the stack.

See Also: IRQs: Hardware Interrupts
          Serial Ports
          BIOS Data Area
          ROM-BIOS Functions
          DOS Functions