"Emergency" must apply to the processor (send an electrical pulse signal) to request "interruption", that is, the processor is required to stop "the job at hand" to process "my urgent" first, this "application" Process, called-interrupt request.
Abbreviation for Interrupt ReQuest, Chinese can be translated into interrupt request. Because each component in the computer will have an independent IRQ, in addition to the PCI card using the PCI bus, each component will occupy an IRQ separately and cannot be reused.
Since the CPU is continuously busy while the computer is running, when the hardware interface device starts or ends sending and receiving messages, and the CPU is required to process information operations, it will send an interrupt request signal to the CPU through IRQ to allow the CPU to store the ongoing work , And then suspend the work at hand, first deal with the requirements raised by the surrounding hardware, this is the role of the interrupt request.
The value of an interrupt request (IRQ, interrupt request) is that there is a special device in the computer that can interrupt it at a specified location when the device sends a signal about its operation. For example, when the printer completes the printing task, it sends an interrupt signal to the computer, and the signal immediately interrupts the computer so that it can judge the next process. If multiple signals are also sent to the computer to request an interrupt, then the computer may not understand it, so each device must set a unique value and its path to the computer. Before plug-and-play (PnP) devices, when adding a new device to a computer, users often had to manually set the IRQ value (or already realized this).
There will be two chips in each system to provide 16 IRQs, most of which have a fixed arrangement. For example, IRQ 0 is fixed as the system timer, and IRQ 1 is the keyboard. Because each IRQ can only be used by one device, the number of IRQs is very limited. If a computer has many accessories, IRQ will inevitably be insufficient, so it may happen that two devices share the same IRQ. There will also be IRQ conflicts, making the device unusable.
The simplest solution is to manually adjust the IRQ allocation in the hardware device manager of the operating system, or make adjustments in the BIOS. If the IRQ is not enough, you can use other methods to solve this dilemma. For example, the PCI bus can share an IRQ, so basically you can add PCI cards, and it will not be restricted by IRQ. The second is to use USB transmission to solve, because the USB control chip will only occupy one IRQ, not all USB products need to monopolize an IRQ, so in theory, up to 127 peripheral products can be connected, and the products that currently have a USB transmission interface are also More and more common. Therefore, peripheral devices that do not require high transmission speeds will gradually develop towards the USB interface in the future.
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