System Overview
1-13
I
nterrupt Assignments
Table 1-3 shows the assignment or availability of IRQ lines.
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
Generated by super I/O controller to indicate that the device con-
nected to serial port 2 (COM2 or COM4) requires service.
IRQ4
Generated by super I/O controller to indicate that the device con-
nected to serial port 1 (COM1 or COM3) requires service.
IRQ5
Available for use by an expansion card.
IRQ6
Generated by super I/O controller to indicate that diskette
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 video controller to indicate that the video or
monitor requires service.
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 hard-disk drive connected to primary EIDE port to
indicate that drive requires service. If the EIDE controller is dis-
abled, 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 not
in use, this line is available for other use.
*
Although the OptiPlex N system board supports up to four EIDE devices, no devices other than
the internal hard-disk drive should be connected.
