KarbosGuide.com. Module 5c2a.

About USB

The contents:

  • What is USB?
  • After a slow start ..

    On the following page:

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  • What is USB?

    USB stands for Universal Serial Bus. It is a cheap and rather slow I/O bus, running at 12 Mbit/sec.

    It can be compared to the FireWire bus, which however is a lot speedier.

    USB is an open and royalty-free specification. Units can be plugged and unplugged on the fly very easily. Here you see the plugs, the two small ones, number two from the left:

    There were problems with USB in the beginning, since many motherboard manufacturers produced their own versions of the port before it was fully standardized. Hence the nickname Useless Serial Bus .

    USB is supported by Windows 95 OSR2.1, Windows 98/Me, Windows 2000 and Windows XP.

    A success

    USB has become a great succes. The bus simplifies PC design - giving us a simple and unified interface for a whole lot of PC units and devices like:

  • Keyboard
  • Mouse
  • Loudspeakers, microphones, and other sound devices
  • Printers
  • Modems and ISDN adapters
  • Scanners and cameras
  • External drives like CD-RWs
  • Card-readers and other adapters

    All these units - and lots of others - will be connected using one single plug at the PC. USB holds up to 127 units in one long chain.

    The keyboard may hold a hub, so other USB units are connected here (although it more often is the monitor to include a hub, as we shall see later):

    Each unit may hold two USB connectors, so they all can be daisy chained.

    This illustration is fiction - I never saw a setup like this, but it shows the intentions of the serial USB interface:

    All units have a firmware identification code, that communicates with the OS (i.e. Windows ). The unit must have a power feed (could be minimum 100 ma) to be recognized by the USB controller and Windows 98. If one unit fails this way, Windows shows an ! on yellow background to signalize that something has to be done. This could be to unplug other USB devices to increase the available power in the chain.

    Many hardware manufacturers today produce their modems, cameras and scanners in versions with two-way interfaces. These devices connect either traditionally using a COM port or using the USB port.

    After a slow start ...

    Personally I always believed, that USB a´´had to become a great renovation of the PC design. However, things were moving very slowly in the beginning.

    Bigger companies like Swiss Logitech (producing the best mice and trackballs available, at least to my opinion) moved very slowly into USB. This probably has been due to serious concern over the correct technical implementations. The COM, PS/2, and LPT ports represent very well-known technology. Replacing them you have to be very certain of the consequences.

    In 1999 and 2000 the USB products became available in large numbers. Many of them are being sold both to Mac and PC. My latest trackball, a Kensington Orbit is only a Mac-product, judging from the box:

    However, the trackball (which is very fine) works fine on any PC with USB. The Windows USB driver instantly recognizes the trackball.

    The same goes for my great little tablet (Wacom Graphire):

    Philips and Logitech - a private vision

    If I were in charge, Philips should go further with USB. Already they build in a USB in their monitors. Why not bundle the monitor with a cordless set of keyboard & mouse. And place the infra-red receiver in the monitor using USB as interface? May I give this idea to Philips:

    Philips even could buy Logitech as well. I think they would fit well together - two fine European vendors.


    You find technical specifications etc. in these sites:

    Intel's USB site http://www.intel.com/design/usb

    USB site: http://www.usb.org

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    Learn more

    Next module (on FireWire and Device Bay)

    Read Module 6a about file systems

    Read about chip sets on the motherboard in module 2d

    Read Module 4d about super diskette and MO drives

    Read module 5a about expansion cards, where we evaluate the I/O buses from the port side

    Read module 5b about AGP

    Read module 7a about monitors, and 7b on graphics card

    Read module 7c about sound cards, and 7d on digital sound and music

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