1. A method for switching a defective signal line with a spare signal line without shutting down a computer system comprising the steps of: monitoring outputs of units configured to determine if a signal line is in error; detecting a defective signal line if said defective signal line has an error rate that exceeds a threshold; and configuring switch control units in a driver/receiver pair associated with said defective signal line to execute a switch of said defective signal line with an indicated spare signal line, wherein said switch control units are configured to control switch units configured to determine which signal line to transmit and receive incoming data.