"There are 50 million PCs out there with USB connector ports. Most of them are totally empty."

That's how Nathan Brookwood, an analyst at the Gartner Group's Dataquest Inc. market-research consultancy, summed up the scant impact the 12-Mbit/s Universal Serial Bus has had in two and a half years of existence. Others put the number of PCs with empty USB host ports as high as 60 million, but according to most industry watchers USB peripherals are on their way.

Slowly at first, but at a gathering pace, all manner of peripherals with USB device ports will begin to roll out. The upshot, according to most observers, is that USB technology will become the standard way to attach monitors, printers, keyboards, mice, fax machines and other, new types of peripheral devices to the PC. "It is beginning to happen, although only in the last month or two," said Brookwood.

The reason for the upsurge is the launch of Microsoft Corp.'s Windows 98 operating system, which is expected to make USB easy to use. Extensive driver support within the OS will make it simple to plug in peripherals and get them up and running straight away, fulfilling the promise of the bus in a way that Windows 95 did not.

"USB developers originally hoped that Windows 95 would do it for them, but the support was lacking. It was a frustrating period," Brookwood said. Now he believes USB's time has come. "We're seeing tremendous numbers of devices being developed," he said: everything from computer-telephony integration systems — an admittedly small market — to what Brookwood calls the "no-think-about" market, including keyboards, scanners, printers and monitors.

Indeed, it is the monitor market that is likely to go to USB first, and Brookwood predicts that 7 million of this year's 10 million USB peripheral sales will be of monitors designed to act as hubs for multiple USB devices daisy-chained into the PC's single or dual USB port.

Why has USB been successfully designed into PCs but not into peripherals?

According to David Fair, Intel Corp.'s manager responsible for Firewire and USB, and the interim chairman of the USB Implementers Forum standards body, the answer lies in energy barriers. "For PC makers it was a lower entry cost and for peripherals makers it was bigger," Fair said. PC makers owe part of that low entry cost to the fact that Intel, after some delays with initial components, offered USB support within its PC chip sets. That left the computer builders with only the additional expense of a USB socket.

"Frankly, Windows 95 is incomplete," Fair said, addressing the software side. "Windows 95 OEM versions were the only ones that supported [USB]. Most peripherals makers would have had to build their own drivers." Fair added: "With Windows 98 you will have a retail pressure, marketing and education." Not to mention greater support for USB peripherals via an expanded set of drivers.

This still leaves developers with decisions about when to use USB interface and controller cores now on offer from intellectual-property vendors, and when to use discrete ICs from the likes of National, Philips and TI.

Chip designers can implement the interface entirely in hardware or move digital processing behind the physical interface into firmware that runs on a microcontroller. Future Technology Devices International (Edinburgh), a fabless chip company, offers discrete devices in a 20-pin dual in-line package based on an embedded 8-bit RISC microcontroller designed specifically for the USB interfacing task. "Protocol handling does imply a microcontroller," said Fred Dart, managing director, acknowledging that the chips are aimed at the simpler end of the peripheral device spectrum. Dart sees the larger chip companies aiming their controllers at hub control and specialized device interfaces such as USB audio, where D/A and A/D converters can be packed on-chip.

For their part, core providers like Sand, Sapien Design, Sican, Simple Silicon, Vautomation and Virtual Chips aim to provide all the support that customers need. Nabil Takla, president and chief executive of Innovative Semiconductors Inc. (Mountain View, Calif.), said, "What you are getting with a microcontroller is flexibility — the ability to change things on the fly. When a chip is pad-limited you tend to go to a hardwired solution. When it's not, a microcontroller gives more flexibility."