What isAPIC

APIC stands for Advanced Programmable Interrupt Controller and it is a highly advanced version of a PIC (programmable interrupt controller). Developed by Intel, APIC is used for managing interrupts in a more advanced manner. It replaced the 8259 interrupt controller and is supported by multiple processors. However, It requires support from the motherboard chipset, BIOS, and an operating system (Windows 2000 and above).

APIC is not just for multiple processors, it is also used on single processor computers because it provides support for virtual PCI IRQs above 15. If you enable APIC, Windows XP takes full advantage and assigns more devices to IRQs above 15.

APIC makes use of a combination of a local APIC built into each system CPU and a set of input/output APICs connected directly to hardware devices. When a hardware device generates an interrupt, it is detected by the IO APIC to which it is connected, and then routed to a specific CPU via the system APIC bus. The operating system knows which IO-APIC is connected to which device and to which particular interrupt line within that device based on a combination of information sources. Together, these two data sets provide information about the entire interrupt hierarchy.

FAQs

What is the function of APIC?

APIC is used for managing interrupts in a highly advanced manner.

Why is APIC used on single processor computers?

APIC provides support for virtual PCI IRQs above 15 and is therefore used on single processor computers.

What is a local APIC?

Local APIC is a feature that is built into each system CPU.

What is an IO APIC?

IO APIC is a set of input/output APICs connected directly to hardware devices.

Conclusion

APIC is an advanced programmable interrupt controller used for interrupt management and is supported by multiple processors. Together with the motherboard chipset, BIOS, and an operating system, it provides support for virtual PCI IRQs above 15. It uses a local APIC and IO APICs for handling interrupts and provides information about the entire interrupt hierarchy through ACPI DSDT and a device’s specific information about its available interrupt sources.

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