Next Previous Contents 16. While the section Troubleshooting lists problems by symptom, this section explains what will happen if interrupts are set incorrectly. This section helps you understand what caused the symptom, what other symptoms might be due to the same problem, and what to do about it.
Performance is likely to be extremely slow.
Both devices will send identical interrupt signals on the same wire and the CPU will erroneously think that the interrupts only come from one device. This will be explained in detail in the following sections. Linux doesn't complain when you assign two devices the same IRQ provided that neither device is in use. The symptoms depend on whether or not you have a modern serial port with FIFO buffers or an obsolete serial port without FIFO buffers. It's important to understand the symptoms for the obsolete ones also since sometimes modern ports seem to behave that way.