System Overview 1-17Interrupt AssignmentsTable 1-3. Interrupt AssignmentsIRQ Line Used By/AvailableIRQ0 Generated by system timerIRQ1 Generated by keyboard controller to indicate that keyboard’s out-put buffer is fullIRQ2 Generated internally by interrupt controller to enable IRQ8through IRQ15IRQ3andIRQ4Generated by super I/O controller to indicate that device con-nected to corresponding serial port requires service (IRQ3 forCOM2 or COM4; IRQ4 for COM1 or COM3)IRQ5 Available for use by expansion card unless this IRQ line is usedby secondary parallel portIRQ6 Generated by super I/O controller to indicate that diskette or tapedrive requires serviceIRQ7 Generated by super I/O controller to indicate that device con-nected to parallel port requires serviceIRQ8 Generated by keyboard controller for each tick of RTCIRQ9 Available for use by expansion cardIRQ10 Available for use by expansion cardIRQ11 Available for use by expansion cardIRQ12 Generated by keyboard controller to indicate that mouse’s outputbuffer is fullIRQ13 Generated by math coprocessor to indicate coprocessor errorIRQ14 Available for use by expansion card unless the IRQ line is in useby the SCSI controllerIRQ15 Available for use
