Waiting for the Universal Serial Bus

by Alan Zisman (c) 1997. First published in Canadian Computer Wholesaler, March 1997

As we?ve said in the past few issues, expect big changes in computer hardware design for 1997. Last issue, we saw how Intel?s MMX multimedia processor additions were the first major addition to their processor instruction set since 1985?s 386.

This issue, we?re going to take you for a ride on the bus?the PC?s expansion bus that is. But like the city bus, a computer?s bus works more or less the same way?but for data signals rather than for commuters. Like commuters, however, your computer?s data signals get on the bus at various places, and get off at their own individual stops?but travel on a single bus along the way. A well designed bus makes sure that a wide variety of passengers can go along for the ride, and that all get where they?re going as quickly as possible.

Your PC has an internal bus, providing connections between the CPU and the RAM, as well as the classic ISA (Industry Standard) 16-bit bus, typically holding your sound card and modem, and the more modern, more powerful PCI bus, for the more demanding video, network, and hard drive connections. PCI provides a 32-bit bus running at 33 mhz, with a peak throughput of 132 megabytes per second. Enhanced PCI versions offering (either) double the speed (fast) or double the width (wide) are possible, but it?s unlikely that we?ll see them put into effect in the near future.

Some PCs have added a SCSI connector to either the ISA or PCI bus?plugging in an expansion card to allow a total of seven devices to be daisy-chained, lined up one after another, at least theoretically with little configuration necessary. This matches the capability that has been standard in Macintosh models since the Mac Plus of 1987. SCSI, however, has never been more than a minority-taste on PCs, partly due to the extra configuration needed to get the SCSI card itself up and running, and the extra cost of the SCSI devices themselves.

Still, PCs users have envied the ease with which Mac owners could plug in add-on devices to their system?s external bus. In the past year or two, we?ve seen the PC?s parallel port being used more and more as a sort of poor-person?s SCSI?devices from Zip drives to QuickCams to Snappy video capture gizmos have all plugged into the computer?s printer port. But like while a clever work-around, the printer port is much slower than real SCSI?my parallel port Zip drive, for example, is less than half as perky as a SCSI model.


This is the year that we should start to see the answer. Systems including the new Universal Serial Bus standard promise to eliminate the need for separate connectors for (count ?em) keyboard, mouse, game, serial, and parallel ports?replacing all with a couple of USB ports. This should produce a cleaner system, with easier configuration, and better performance.

A typical PC is limited to two parallel ports and four serial ports?and the serial ports are limited to a throughput of 115 kilobits per second. By comparison, up to 127 devices can be connected to a USB port, with data travelling at 12 megabits per second. The four-pin USB connector includes two powered pins, so that plugged-in devices won?t need external power supplies. The first device plugged in, perhaps a keyboard, will act as a hub?additional devices will be plugged into it, not directly into the computer. (Some USB devices, such as mice, should be hubless?able to plug directly into the system. And yes, Mac users, the longtime Apple Desktop Bus (ADB) has enabled you to plug your mouse into your keyboard?but with much less power and speed than USB will offer. Try plugging your scanner or printer into your Mac?s keyboard!)

USB supports hot plugging and plug and play?that means that devices can be plugged in while the computer is running, and that the operating system will (hopefully!) identify the devices, and provide drivers as needed.

USB hardware is included on a few models from major manufacturers?the IBM Aptiva S78 and Toshiba Infinia, for example. New Pentium and MMX motherboards have pins allowing for easy addition of USB ports, but typically (as of early 1997), OEMs are not yet including the USB ports themselves. Here we have a classic chicken and egg dilemma?there aren?t many USB devices available yet? the Toshiba model ships with a USB keyboard, but the Aptiva or the USB-capable Sony PCV-90 don?t come with anything to plug into the new port. And until recently, there hasn?t been any system-level software support for USB?Toshiba had to write proprietary drivers.

Even Microsoft?s recent OEM-SR2 (Service Release 2) version of Win 95 lacked USB support?now, however, Microsoft has released a patch for SR2 that provides this support. More class device system drivers are expected to be built into Microsoft?s two 1997 operating systems?Memphis (Windows 97) and NT 5.0, just beginning testing for release dates later this year. These make it easier to add create drivers for specific classes of peripherals?cameras, speakers, scanners, what-have-you. A single USB connection could support all of these, along with high speed cable modems or ADSL modems, which currently need to be plugged into an Ethernet card.

But even with support in the operating system, it?s going to take a while for peripheral devices to trickle onto the market? a number were shown at last Fall?s Comdex, including monitors from Sony, NEC, Daewoo, and more. Canon showed off a USB printer, while several manufacturers showed off keyboards. Panasonic has promised a USB digital camera and a USB speaker, early in 1997.

As a result of this tentativeness from the motherboard manufacturers, peripheral manufacturers, and Microsoft, It will be a couple of years before we?ll be able to entirely do away with the mess of conventional ports and wires.

My suspicions? USB won?t be a serious contender until later in 1997 at the earliest. Buyers should not, however, buy a system that isn?t USB-ready?at a minimum, they should be able to add USB ports onto their new system when operating system and peripheral support becomes more of a reality. OEMs need to make sure that the systems they?re shipping provide such potential.

USB isn?t the only new bus architecture, however. Also expect to see AGP (Accelerated Graphics Port) to speed up bottlenecks in today?s graphics adapters, and Firewire (at least, not another three letter acronym). Officially called IEEE 1394 (I?ll keep calling it Firewire, thanks), it provides an external bus starting at 100 Mbps (compared to USB?s 12 Mbps). More on these next month.

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Alan Zisman is a Vancouver educator, writer, and computer specialist. He can be reached at E-mail Alan