New Technology: USB 2.0

The June 2002 issue of Smart Computing has an article focused on a new hardware technology for the personal computer, the USB 2.0 standard serial bus.

The ability to connecting peripherals to a PC is important. The keyboard, mouse, and printer are the old mainstays, but do not require the bandwidth needed by today’s image intensive applications and devices. The original RS-232C serial port, introduced in 1969, offered a 20 kilobit-per-second (Kbps) bandwidth. Using an 8-bit character set and 500 characters per typewritten page, this serial port could support 5 pages of text per second, which was more than fast enough.

Devices, such as scanners and CD burners, require more bandwidth to work at acceptable speeds. A CD-R can hold 700 megabytes (MB) of information. At 20 Kbps, burning a CD in a burner connected to a RS-232C serial port would take almost 78 hours. A faster connection was needed.

The original USB (Universal Serial Bus) was introduced in 1996. Now known as USB 1.1, this bus technology could support 127 devices at a bandwidth of 12 (megabits per second) Mbps. At that speed, the burning a CD would take just less than 8 minutes, at least in theory. In addition, the devices were now hot swappable, meaning that a device can be connected or disconnected while the PC is running. With an RS-232C serial port connection, the device had to be connected and turned on before the PC was started in order for the PC to recognize the device.

USB 1.1 still lagged behind the IEEE 1394, commonly known as FireWire, transfer rate of 400 Mbps. However, IEEE 1394 only can support 63 devices. Even with this limitation, FireWire was a much more appealing alternative for those who needed high-speed connections between devices and the PC.

In 2000, a new USB standard was introduced, although it is just starting to be commonly used. This new USB standard, called Hi-Speed USB or USB 2.0, is forty times faster than USB 1.1, delivering a bandwidth of 480 Mbps. Although it is so much faster than USB 1.1, in actual practice the new USB devices can burn a CD only six times faster than the original USB, due to device and hardware limitations. In theory, a CD burner connected to a USB 2.0 port could burn a CD in just less than 12 seconds.

USB 2.0 is not without restrictions. USB 2.0 cables must be no more than 5 meters in length, and the port can only supply 500 milliamps (mA) of operating current. If a hub is used, to allow multiple devices to use one port, the full operating current may not be supplied to each device. It is best if higher-power devices, such as scanners, CD burners, and digital camera, are self powered to guarantee an ample supply of power.

If longer than a 5-meter run is needed, a series of 5-meter cables and hubs (self-powered, I assume) can be daisy-chained together to create a longer run. The OrangeUSB 2.0 Hi-Speed Hub can support four additional hubs, allowing a 30-meter run.

USB 2.0 has not been quickly accepted. This high-speed USB was a “coming soon” attraction for years at trade shows. But IEEE 1394 was already available. And it took a while for device manufactures to create the scanners, CD burners, digital cameras, etc, that take advantage of the new technology. As of the writing of the article, there were 37 vendors with USB 2.0 devices on the market or soon to be on the market.

Computer manufacturers have been slow in adding the USB 2.0 ports. Gateway was the first with a PC with the new USB ports. These PC were just introduced in January 2002. PCI-based USB 2.0 adaptors have been available, and currently sell for between $40 and $90. But even adding an upgraded port may not be enough. The PC must be USB compliant. Most PCs manufactured after 1997 are. According to the article, “the new USB isn’t likely to become universal, however, until chip manufacturers add USB 2.0 to their product lines later this year.”

The PCI-based USB 2.0 cards each have at least one internal port. The article does not mention why, but just as we have seen a shift to USB keyboards and mice, there may be plans for connecting internal devices, such as floppy and CD drives, to a USB port instead of the IDE connector.

And the operating system may not support these ports. According to the article, no “OSes (operating systems)…include native driver support for Hi-Speed USB.” Microsoft has a USB 2.0 driver update that can be downloaded, but only for WinXP. An update for Win2000 is planned. There are no plans to provide support for Win98 or WinNT. Even if you purchase a port with driver software, chances are it will only run on Win98 or later. There does not seem to be any support for those still running Win95.

The best news for PC owners is the forward and backward compatibility of USB 1.1 and 2.0. The physical ports are identical. Any USB 1.1 device will run in a USB 2.0 port, and any USB 2.0 device will run in a USB 1.1 port, although only at the 12Mbps rate. This is good news since new devices do not have to be purchased when upgrading the USB ports (or purchasing a new computer). And a new device requiring the USB 2.0 port can be purchased and used on an older PC with only USB 1.1 until the new PC can be purchased. In my experience, it is not often that you can reuse a device purchased for your previous PC.

Will USB 2.0 eat away at the IEEE 1394 market? As of August 2000, 99% of PCs could support USB 1.1. Projections are there will be 750 million USB-enabled systems by the end of 2004. IEEE 1394 FireWire does not have that enjoy the same broad base, although it does have a solid following in the consumer electronics market with digital video camcorders. Even WinXP offers support for FireWire. And a new 800 Mbps IEEE 1394 standard is planned. But according to the USB Implementers Forum, “while the two serial buses are similar, they are intended to fulfill different bandwidth and cost needs.”

My prediction is that USB 2.0 will gain a strong foothold and virtually eliminate FireWire’s embedded market. I say this because of history. My first scanner connected through the PC’s parallel port. It offered 150 Kbps bandwidth. And it was slow and the scanner had to be on before the PC was booted in order for the scanner and printer (which was connected to the scanner’s parallel port) to be recognized by the system. With the price drops, I was able to purchase a better USB scanner for less than the cost of an additional parallel port. Then in 1990 I went to an IBM presentation for their SCSI “Scuzzy” drives. These offered respectable speeds of 4 to 80 Mbps. SCSI devices, from scanners to Zip drives, were very common in the mid to late 1990’s. Now you really have to search for one. USB, as was mentioned, is universal in the PC market. And this new USB standard will only continue the dominance.

Resources

“Say Hello to the New Bus: USB 2.0 Sets a New Standard”. Smart Computing. June 2002. pp. 29-31.