Here is the same example again, however this time a BIOS Hwi is being used to process the interrupt service routine. Because the Hwi was configured with software interrupts enabled, it disables Swis at the beginning of the ISR and re-enables them at the end. Now the world makes sense again; the higher priority Swi preempts the lower priority Swi, but both get preempted by the highest priority Hwi. For more information regarding BIOS Hwis, please see the hardware interrupts module of this training series.