Understanding Universal Serial Bus, USB

Michael P. List 

     Humans have three basic emotions, greed, greed and greed!  If a BMW will allow me to go 125 MPH, why should I buy a KIA that will only go 60, down hill, with the wind on its side? Especially if they cost the same! Point: USB devices send and receive data 100 times faster than RS-232 serial and 25-pin parallel. 

     First let’s discuss the brief history of USB. With the on slot of literally hundreds of peripheral devices available for computers, it became apparent to the industry that a new means of connecting these devices was needed. Serial and parallel connections were severely limited slow speed and the amount of devices that could be connected at one time.   The Universal Serial Bus, USB 1.1 was introduced by a consortium of peripheral manufacturer’s including IBM, Microsoft, Compaq, NEC, Intel, DEC and Northern Telecom to address this problem.  In 1966 the first USB 1.1 connection was offered in new PC systems.  Another want-to-be standard, FireWire IEEE 1394, was also being developed reaching speeds of 400 Mbps (Megabits per second), compared to USB 1.1 running at 12Mbps.  Although FireWire was much faster, it was also more costly. The average device using FireWire technology could cost up to five times as much as a compatible USB device. 

     OK, I’ll play your silly game; I’ll build a KIA that can run 20 MPH faster than your BMW! That’s exactly what USB 2.0 was created to do.  The newest standard for connecting peripheral devices is currently USB 2.0 with a top speed of 480 Mbps, forty times faster than the original USB 1.1. There is confusion throughout the industry and public as to what this new standard should be called.  The USB-IF, the consortium that maintains the USB standard would like to see the numbers, 1.1 and 2.0 simply go away. They prefer manufacturers use the logo’s that depict the certified USB, considered Full-Speed (1.1), and certified USB, Hi-Speed for the 2.0 standard.  Wow…you mean I can attach a USB device and get 480 Mbps transfer rate?  No. If you purchase a USB device, note the fine print, in most cases the manufacturer will advertise anywhere between 5 and 15 times faster than USB 1.1 and hundreds of times faster than serial or parallel devices. This is because USB 2.0 is still new and manufacturers do not use the full potential of the standard.

     USB devices have a number of advantages over serial and parallel devices.  With serial and parallel you were limited to between four and six devices. In order to add additional external devices you would need to disconnect an existing device and connect the new device.  Switching devices in this manner became time consuming and a real headache for users. Enter USB; you now have the ability to connect up to 127 devices.  That’s 120 more external devices then you could connect the day before you started using USB.  Simplicity of installation; USB devices use one, simple to install, cable that is keyed so the user can not plug the connector into the wrong slot.  For the exception of sheer number of devices, the best advantage of USB is its Plug-and-Play capability in Windows and Macs.  USB devices are manufactured to be “Hot Swappable”, that is they can be plugged into the PC while the computer is running.  Be cautious here, although they can be plugged and unplugged while the PC is on, initial installation will vary.

     Installing a USB device for the first time can be trying. It is important to read the instructions that are packaged with your new USB product to find out how to install it.  IMPORTANT NOTE:  I understand that you simply can’t wait to plug in your new USB device, but remember, most USB devices must have drivers installed prior to actually plugging in the device.  This is the most common problem associated with USB installation.  Check and recheck the documentation that comes with your device to find out if the drivers need to be installed first.  You must also have a compatible operating system in order to use USB.  Windows98 and below do not have USB support, Windows98 second edition (except NT) and above support USB devices.

     I do not have 127 USB connections on my PC so how can I connect that many? Although I doubt you will ever need to install 127 devices, it is possible, simply use all the available USB connections, most PC’s will have connections for between four and eight USB devices. Once you have used them up, purchase a USB HUB, this will allow you to add additional devices.  I do not advise using USB for networking, it is possible, but remember that USB is limited to about four meters in length and you will still need some type of USB HUB. The conventional RJ-45 CatV cable, Ethernet card and RJ-45 Hub are still your best bet for small local networks.

     USB is here to stay, at least until something quicker, faster and cheaper comes along.  Ease of installation, number of connections and speed make USB 2.0 the external peripheral standard of choice.