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.[1][2]

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.