Home » Questions » Computers [ Ask a new question ]

difference between IRQ and Interrupt Priority level

difference between IRQ and Interrupt Priority level

Can someone tell me if the IRQ of a device is different to the Interrupt Priority level?

Asked by: Guest | Views: 33
Total answers/comments: 1
Guest [Entry]

"An IRQ is an hardware interrupt request from a device. It is a hardware signal with alerts the CPU that external hardware wants it's attention. The interrupt usually causes the CPU to immediately stop what it was executing and jump to different code, usually an interrupt service routine that was registered earlier.

Then once the CPU is executing an interrupt service routine, what should happen when another interrupt request comes in while the CPU is processing a different interrupt? Interrupt priority level is what answers that question. The simplest priority seem, as pointed out in Wikipedia, is an interrupt disable setting. So while servicing an interrupt, all other interrupts will not interrupt the processor (they will no be lost, they will be serviced once the current service routine is finished). With more complex priority scheme, some interrupts will interrupt others.

For example, maybe the hard drive interrupt has a higher level than the keyboard, since the hard drive speed is important and no one is going to notice a < 1ms delay in processing a key press."