An Interrupt Request (IRQ) is a signal sent by a hardware device to the processor of a computer system to request attention or notify it of an event that requires immediate processing. IRQs are an essential mechanism for managing hardware interrupts in a computer system and allow devices to interrupt the normal execution of the processor to handle critical tasks or events.
Here are some key points about Interrupt Request (IRQ):
- Hardware Interrupts: Hardware devices, such as keyboards, mice, network cards, and disk drives, can generate interrupts to communicate with the processor. When a device wants to gain the attention of the processor, it asserts its corresponding IRQ line.
- IRQ Numbers: Each hardware device connected to the system is assigned a unique IRQ number, which represents a specific interrupt line. In older systems, IRQs were numbered from 0 to 15, while modern systems may have more IRQ lines available.
- Interrupt Controller: An interrupt controller, typically integrated into the motherboard or chipset, manages and prioritizes interrupts from various devices. It receives interrupt signals from devices and forwards them to the appropriate CPU core for handling.
- Interrupt Handling: When an IRQ is triggered, the processor suspends its current execution and transfers control to the Interrupt Service Routine (ISR) associated with that particular IRQ. The ISR is a software routine that handles the interrupt, performs necessary operations, and restores the interrupted execution afterward.
- Interrupt Prioritization: IRQs are prioritized to ensure that critical interrupts are handled first. Lower priority interrupts may be temporarily masked or delayed to allow higher priority interrupts to be processed promptly.
- Interrupt Sharing and Conflict: Multiple devices may share the same IRQ if they can be serviced simultaneously or if they generate interrupts infrequently. However, conflicts can arise if two devices require attention at the same time, resulting in system instability or device malfunction.
- IRQ Assignments: IRQ assignments are typically managed by the operating system or system BIOS. They can be configured manually or automatically by Plug and Play (PnP) systems, which dynamically assign IRQs based on device requirements and system availability.
IRQs play a crucial role in the proper functioning of hardware devices and ensure efficient communication between devices and the processor. By using IRQs, hardware devices can interact with the CPU in a synchronized and controlled manner, allowing for timely processing of critical events and efficient utilization of system resources.