Fast interrupt request

Fast Interrupt Requests (FIQs) are a specialized type of Interrupt Request, a standard technique used in computer CPUs to deal with events which need to be processed as they occur such as receiving data from a network card, or keyboard or mouse actions. FIQs are specific to the ARM CPU architecture, which supports two types of interrupts; FIQs for fast, low latency interrupt handling and Interrupt Requests (IRQs), for more general interrupts.

An FIQ takes priority over an IRQ in an ARM system. Also, only one FIQ source at a time is supported. This helps reduce interrupt latency as the interrupt service routine can be executed directly without determining the source of the interrupt. A context save is not required for servicing an FIQ since it has its own set of banked registers. This reduces the overhead of context switching.