A computer system with a SCSI backplane board has duplex-ready logic for switching the computer system between a SCSI simplex mode and a SCSI duplex mode. The duplex-ready logic includes a set of bus quick switches, a duplex-ready logic controller, and a set or sets of active terminators. The SCSI simplex mode and SCSI duplex mode are configured by the duplex-ready logic controller based on the number of SCSI cables present. If only a primary SCSI cable is present, the duplex-ready logic controller enables a SCSI simplex mode. To enable a SCSI simplex mode, the bus switches are enabled and the terminators are selectively enabled and/or disabled. If a primary SCSI cable and a secondary SCSI cable are present, the duplex-ready logic controller enables a SCSI duplex mode. To enable a SCSI duplex mode, the bus switches are disabled and the terminators are selectively disabled and/or enabled. The duplex-ready logic controller optionally may change to SCSI identification values for a set of SCSI devices for a SCSI duplex mode and restore the SCSI identification values for a SCSI simplex mode. In manually configuring the state of the SCSI backplane for the secondary SCSI duplex mode, the chassis is minimally disassembled to allow for installation of a SCSI cable from a secondary SCSI controller to the SCSI duplex-ready backplane board. The SCSI duplex-ready backplane board both eliminates the need for a board changeout and a duplex-option kit and reduces the disassembly and reassembly required to configure the state of the SCSI backplane of a computer system for a SCSI simplex mode or a SCSI duplex mode.