Newbury, Berkshire-based Compass Computer Group Ltd is shipping the ClusterPort/S, which enables a personal computer to support up to 128 serial input-output ports using one expansion slot: manufactured by Nashville, Tennessee-based company, Arnet Inc, it is designed for use with AT, EISA or Micro Channel architectures and consists of an adaptor board located in the host personal computer, an external power supply and an RS-422 link supporting up to eight external 16-port concentrator units operating as input-output subsystems; it is priced at UKP1,600 for 16 ports including a host adaptor, each additional 16-port concentrator costs UKP1,060, and accommodates up to eight concentrators per board.