If the IRQ for a device driver is changed from 9 to 2, some devices do not function correctly (for example, modems). Use the DCU to change the IRQ value back to 9. In particular, when the jumper is set to 2 on an AT bus system, the IRQ should be set to 9. If the IRQ value is 9, do not change it. If the IRQ value is 2, change it to 9.