Redirection Table Entry

An IOAPIC is a piece of hardware that receives interrupt signals from devices on a bus and redirects these interrupts as messages to a CPU.

Devices on the bus are known as I/O devices, hence the term IOAPIC. The APIC component in a CPU is known as a LAPIC, or Local APIC.

Redirection Table

The redirection table in an IOAPIC contains information AbOUT how to forward interrupts from each interrupt signal line on the IOAPIC. The redirection table is programmable.

Redirection Table Entry

Each entry contains the following information for each interrupt signal line:

Whether the line is masked (enabled)
Whether the line should be edge or level triggered
Signal polarity for level interrupts: ACTIVE when low or active when high
Which CPU(s) the interrupt should be routed to
How the target CPU(s) should deliver the interrupt to software, including
Which legacy interrupt vector the target CPU(s) should route the interrupt to (effectively controls priority)

See also