Question: IRQ and how it works

Question

Hello folks,

I am following an advice from someone that told me to get better, learn how the system works. Therefore, here is my question: How does IRQ works?

From what I understand - it is only assumptions, IRQ are interruption to the CPU coming from one of the connected components. Each one have different levels of interruption, therefore they are treated differently when they happens. Software interrupt are lower priority than hardware. Each components have a direct channel with the CPU in case they need to throw an interruption.
As I understand, the ICH and MCH does act has messenger to the CPU.

Now, why they are throwing interruption could be because they receive data or others. The error rising from an interruption can come from corrupt pointers(?) .

This is assumption and I am trying to make sure I understand this part properly instead of guessing how it really do.

source link: https://social.technet.microsoft.com/Forums/windows/en-US/a4de59de-633a-44da-800b-aa1a48abd403/question-irq-and-how-it-works?forum=winservergen

Answer 1

How IRQ Works

The first thing we have to know is that every expansion slot, every device or controller on the motherboard has one wire implemented which we call theinterrupt wire. This wire is typically labeled as “INT”, and it is attached to the CPU. Whenever current is applied to the interrupt wire, the connected device gets the CPUs attention. The INT wire goes to the specific pin on the CPU. When the CPU detects the current on that pin, it will try to service the requesting device.

The problem is that the CPU only has one physical interrupt connector, and the CPU typically has to service a lot of devices on the system. All systems today have more than one device. To accommodate multiple devices we actually use additional chip called the Programmable Interrupt Controller (PIC). The PIC is placed between the CPU and other devices in the system. The interrupt wire from each device is connected to the PIC chip. That way we have multiple devices which can interrupt the CPU over the PIC chip.

Regards,
Anne