Fast interrupt request
ARM architecture supports two types of interrupts: fast interrupt requests (FIQs), for fast, low latency interrupt handling and Interrupt Request (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 FIQ since it has its own set of banked registers. This reduces the overhead of context switching.