Dell OptiPlex GXi, Service Manual

Page: 41 / 147

System Overview 1-23
I
nterrupt Assignments
Table 1-3. Interrupt Assignments
IRQ Line Used By/Available
IRQ0 Generated by system timer.
IRQ1 Generated by keyboard controller to indicate that keyboard’s out-
put buffer is full.
IRQ2 Generated internally by interrupt controller to enable IRQ8
through IRQ15.
IRQ3 Available for use by an expansion card.
IRQ4 Generated by super I/O controller to indicate that the device con-
nected to the serial port (COM1 or COM3) requires service.
IRQ5 Available for use by an expansion card.
IRQ6 Generated by super I/O controller to indicate that diskette or tape
drive requires service.
IRQ7 Generated by super I/O controller to indicate that device con-
nected to parallel port requires service.
IRQ8 Generated by keyboard controller for each tick of RTC.
IRQ9 Available for use by an expansion card.
IRQ10 Available for use by an expansion card.
IRQ11 Available for use by an expansion card.
IRQ12 Generated by keyboard controller to indicate that mouse’s output
buffer is full.
IRQ13 Generated by math coprocessor to indicate coprocessor error.
IRQ14 Generated by device connected to primary EIDE port to indicate
that device requires service. If the EIDE controller is disabled,
this line is available for other use.
IRQ15 Generated by device connected to secondary EIDE port to
indicate that device requires service. If the EIDE controller is
disabled, this line is available for other use.
NOTE: The built-in sound controller, built-in NIC, and built-in video controllers are
assigned available IRQs automatically during system start-up.