Future personal computers will support a new low speed bus suitable for interfacing to peripheral devices such as keyboards and mice

Because of the numerous peripheral interfaces to a PC, system integrators have to contend with a mess of cables and connectors outside the box. Now, a consortium of computer companies, including Intel, Microsoft, Compaq and IBM have come up with a solution to the problem called USB, or the Universal Serial Bus. The promise is that it will bring to an end the cable nightmare for good.

The USB provides PCs with a new bus with a bandwidth of 12 MBits/sec, so that mice, keyboards, printers, monitors, loudspeakers and joysticks can all be simply connected to the PC with a standard cabling system.

On the hardware front, new PC motherboards will come with a pair of USB connections on them. Operating system support comes from Microsoft, who has committed to support the USB interface in its Windows and Windows NT software. Silicon support for the bus is available from Philips Semiconductors, Intel and Cypress Semiconductor.

USB uses a `tiered star topology’ which means that some USB devices – called USB `hubs’ – can serve as connection ports for other USB peripherals. Only one device needs to be plugged into the PC. Other devices can then be plugged into the hub.

USB hubs may be embedded in such devices as monitors, printers and keyboards. Stand-alone hubs could also be made available, providing a handful of convenient USB ports, right on the desktop. Hubs feature an upstream connection as well as downstream ports to allow the connection of additional peripheral devices.

USB host controllers manage and control the driver software and bandwidth required by each peripheral connected to the bus. Like USB host controllers, USB hubs can detect attachments and detachments of peripherals occurring downstream and supply appropriate levels of power to devices.