Arrangement for expanding the device capacity of a bus

An arrangement (FIG. 1) that allows banks (15,25) of up to eight duplicated active devices (30-37,40-47) to be connected to a SCSI bus (14) and to share SCSI device IDs, and also allows multiple hosts (10,20) to share the SCSI bus and the connected active devices. Tri-state buffers (200) act as gates (13,23,38,48) to interface host adapters (12,24) of a plurality of hosts, and active devices of a plurality of device banks, to the SCSI bus. The gate of only one host adapter and the gates of only one bank of devices are enabled at any one time. Only the devices of the enabled bank can receive and respond to addresses from the SCSI bus, while the devices of the other banks are prevented from receiving and responding to addresses from the SCSI bus. Each host has a tri-state buffer acting as bank selector (16,26) for selecting one of the device banks, by enabling the gates of the devices of the selected bank through a bank select bus (50). Only one host's bank selector is enabled at any one time.