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OS X and iOS Kernel Programming by Douglas Clarke, Ole Henry Halvorsen

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Interrupts

Interrupts provide a mechanism for PCI and other hardware devices to signal the CPU asynchronously when an event of interest occurs, such as when a key on a keyboard is pressed or when the position of the mouse is moved or its buttons clicked. A web camera might send an interrupt every time a new video frame becomes available, which will allow its driver to know when the new frame can be read from its mapped memory region. Interrupts save the CPU from polling each device to determine if new data is available. Legacy PCI devices used dedicated interrupt pins that were physically wired from the PCI card/slot to a pin on the CPU. More modern Thunderbolt and PCIe-based technologies use message-signaled interrupts (MSI), avoiding the need ...

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