Take This CompTIA A+ Essentials Quiz On IRQ Assignments!

Com (usually serial) ports 2 and 4 use IRQ 3. IRQ 4 is used by the other two (COM1/COM3).

Com ports 1 and 3 use IRQ 4. COM2/COM4 use IRQ 3, the lower-numbered (and higher priority) interrupt request.

IRQ 0 is used for the system timer. IRQ 8 is the Real-Time Clock.

The correct answer is IRQ 6. IRQ stands for Interrupt Request and it is a signal sent by a hardware device to the CPU to request attention. In the case of the floppy disk controller, it is assigned IRQ 6. This means that when the floppy disk controller needs to communicate with the CPU, it will send an interrupt request on IRQ 6.

IRQ 8 is used by the real-time clock. The real-time clock is responsible for keeping track of the current time and date in a computer system. It is an essential component for various time-sensitive operations and functions. By utilizing IRQ 8, the real-time clock can interrupt the processor when it needs to update or synchronize the system time. This ensures accurate timekeeping and synchronization with other devices in the computer system.

Early in PC development, only IRQs 0-7 existed; lower numbers were assigned higher priority. When additional IRQs were needed, IRQ 2 was modified to accept signals from IRQs 8-15, to allow higher-numbered IRQs to obtain a higher priority.

The correct answer is IRQ 15. IRQ stands for Interrupt Request and it is a signal sent to the processor to inform it that a device needs attention. The secondary IDE controller is responsible for connecting secondary IDE devices such as CD/DVD drives or additional hard drives. IRQ 15 is commonly assigned to the secondary IDE controller in order to enable communication between the controller and the processor.

The correct answer is IRQ 1. The keyboard uses IRQ 1 as its interrupt request line. IRQ stands for Interrupt Request and it is a signal sent to the processor to request attention or to interrupt its current operation. The keyboard sends an interrupt signal to the processor when a key is pressed, and this signal is assigned to IRQ 1.

Although IRQ 12 can be free if no PS/2 mouse is present, it is in use, by default, when a standard mouse is attached. USB mice do not occupy this interrupt, if installed.

While IRQ 13 was used on legacy systems to control portions of the ISA bus, it is now used by the math coprocessor integrated into all modern CPUs.

IRQ 5 is used by the LPT2 device. IRQ stands for Interrupt Request and it is used by devices to request the attention of the CPU. LPT2 refers to the second parallel port on a computer, which is used for connecting printers and other parallel devices. Therefore, the correct answer is LPT2 as it correctly identifies the device that uses IRQ 5.

The IRQs assigned to printer (LPT) ports are IRQ 7 and IRQ 5. These IRQs are commonly used for parallel ports, such as printer ports. IRQ 7 is typically used for the first parallel port (LPT1) and IRQ 5 is used for the second parallel port (LPT2). These IRQs are responsible for managing the communication between the printer and the computer, allowing data to be sent and received effectively.

IRQ 9 is free, despite being "cascaded" to IRQ 2; it has no default assignment. IRQs 10 and 11 have no default assignment or other role at all.

The only IRQs that are actually reserved by the system are IRQ 0 (System timer) and IRQ 1 (keyboard). IRQ 2 "cascades" with IRQ 9, such that the system will see these as the same assignment; they are not, however, technically "reserved". IRQ 8 is used for the Real-Time Clock, but is not reserved either.

It is worth noting that IRQ 1 is always reserved for a keyboard, even if no keyboard is present or needed.