Automatic selection of an upgrade controller in an expansion slot of a computer system motherboard having an existing on-board controller

Abstract

A computer system that automatically detects and configures an upgrade peripheral controller(s) when present in an expansion slot(s) during the computer system startup, or otherwise, enables and configures an on-board peripheral controller(s). The selection of either a peripheral controller on the computer system motherboard or an upgrade peripheral controller plugged into an expansion slot is automatically determined during startup of the computer system. The logic circuit and software used to accomplish this automatic selection do not degrade the performance of the selected peripheral controller during normal operation of the computer system since non-critical timing direct current (DC) level signals are utilized. No additional logic gates which could cause additional time delays are introduced into critical timing signal paths. No hardwired jumpers are needed nor desired for automatic selection of the desired peripheral controller during startup of the computer system.