High performance mainframe computer cables

The mainframe computer is a fascinating combination of various packaging technologies including multichip modules, card-on-board assemblies, DC-DC power supplies, and high performance cable assemblies. Advances in chip technology along with higher density first and second level packaging have reduced the number of cables used in mainframe computers while the performance requirements for cables have continued to increase. High performance mainframe cables have evolved over the years from simple transmission line ribbon cables to custom discrete mini-coax cables. The latest evolutionary change is a spin-off from the standard SCSI style cable referred to as the STI cable. The STI (self timed interface) cable is a hybrid 'SCSI style' cable used in the latest IBM S/390 mainframes. The STI cables use standard 50 pin SCSI connector hardware and a 22 pair bulk wire to provide up to 330 Mb/s data transfer rates for each of the differential pairs in the cable. The cables are used for both internal and external connections between processors and provide 8 bit data in and data out paths as well as parity and clock signals. Performance results of the cable demonstrate the delicate balance required to satisfy the conflicting electrical and mechanical requirements for the interconnection.