USB was initially designed to overcome the barriers of both the maximum speed of 115,000 bps with serial ports, and signal skew with longer parallel cables.
Signal skew is the process of parallel bits arriving at the destination out of synch. (This problem has been overcome with the parallel ATA drives with the onset of the newer SATA (serial ATA) technology.
USB version 1.1 characteristics
1 or 12 Mbps
A maximum of 127 Hot swappable devices.
Offers a tiered-star topology, 5 levels deep (including the Root hub)
Any USB extension is considered a tiered hub.
Maximum cable length is 5 meters.
This may easily be confused with a Star/Extended star Ethernet physical topology on a test question. It is not.
It is also important to understand that each device is allocated bandwidth, therefore the greater the number of devices the less bandwidth each device has available. The devices are sharing the USB Bus.
USB version 2.0 Characteristics
480 Mbps
A maximum of 127 Hot swappable devices.
Offers a tiered-star topology, 5 levels deep (including the Root hub)
Any USB extension is considered a tiered hub.
Maximum cable length is 5 meters.
USB 2.0 is 40X faster than Version 1.1
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