Matt Trask
A new USB (universal serial bus) that supports a maximum of 12 Mbps could become a standard PC connector next year and eventually eliminate the mess of cables found behind today's PCs.
Like other serial-bus standards, such as Access.bus, Apple's GeoPort, and P1394 (also called FireWire), USB allows you to connect multiple devices through a single connection to a PC. But USB's maximum 12 Mbps makes it better suited for CTI (computer telephony integration) applications than Access.bus, which tops out at 100 Kbps. USB will cost less to implement than P1394, and it's backed by Compaq, Digital Equipment, IBM PC Co., Intel, Microsoft, NEC, Northern Telecom, and likely other companies in the future.
The most important aspect of USB is its ability to handle multiple i
sochronous data streams, which means multiple devices can operate concurrently with guaranteed throughput and data latency. Asynchronous operation is possible for devices that don't require guaranteed bandwidth. USB also permits the hot-plugging of multiple devices, such as modems, telephone switches, CD-ROM drives, multimedia audio devices, and tape backup systems, through a single four-wire connector. The interface supports up to 64 devices (one being the host computer itself).
Automatic-configuration software built into Windows 95 (though not necessarily the first release of Windows 95) will provide Plug and Play functionality for these external devices, allowing slotless, low-profile system designs that can be customized by unsophisticated users. USB's promoters say that laptop computers with USB connectors will easily connect through one port to a future generation of standard desktop peripherals without requiring a docking station.
Compaq, DEC, and IBM say they will support USB in future P
Cs, and NEC and Northern Telecom plan to build USB support into their future telephone devices. USB backers say the first PCs with built-in USB connectors should appear in early 1996. USB support has been promised for, in addition to Windows 95, Windows NT and IBM's OS/2 Warp.
One advantage that USB has over competing standards is its price. Jim Pappas, USB program manager at Intel (Hillsborough, OR), says future PCI (Peripheral Component Interconnect) chip sets from the company will support USB at no additional cost over that of current chip sets. (Texas Instruments currently sells its $1394 physical-layer and logical-layer chips for a combined price of approximately $30 each in 1000-unit quantities.) Intel will also make USB chips for peripheral manufacturers. Pappas predicts that USB connectors, which will be made by other companies, will cost system manufacturers a mere 35 cents per PC.
Intel officials say USB will likely coexist with other PC peripherals, such as current keyboards, mice, an
d serial and parallel ports, but they predict that USB will eventually replace all those ports and their associated wires. "We're quite confident we'll have USB on every computer," Pappas says. "And the way you make something universal is to put it on the motherboard."
SERIAL BUSES COMPARED
STANDARD PEAK BANDWIDTH
Access.bus 100 Kbps
GeoPort 2 Mbps*
P1394 100-400 Mbps
USB 12 Mbps
*Mac serial communications controller implementation.
Vendors Ride Bus to Better Telephony
