Speed
To allow high-speed (USB 2.0) devices to operate in their fastest mode all hubs between the devices and the computer must be high speed. High-speed devices should fall back to full-speed (USB 1.1) when plugged in to a full-speed hub (or connected to an older full-speed computer port). While high-speed hubs can communicate at all device speeds, low and full-speed traffic is combined and segregated from high-speed traffic through a transaction translator. Each transaction translator segregates lower speed traffic into its own pool, essentially creating a virtual full-speed bus. Some designs use a single transaction translator, while other designs have multiple translators. Having multiple translators is a significant benefit when one connects multiple high-bandwidth full-speed devices.
It is an important consideration that in common language (and often product marketing) USB 2.0 is used as synonymous with high-speed. However, because the USB 2.0 specification, which introduced high-speed, incorporates the USB 1.1 specification such that a USB 2.0 device is not required to operate at high speed, any compliant full-speed or low-speed device may still be labelled as a USB 2.0 device. Thus, not all USB 2.0 hubs operate at high-speed.
Read more about this topic: USB Hub
Famous quotes containing the word speed:
“The greatest felony in the news business today is to be behind, or to miss a big story. So speed and quantity substitute for thoroughness and quality, for accuracy and context. The pressure to compete, the fear somebody else will make the splash first, creates a frenzied environment in which a blizzard of information is presented and serious questions may not be raised.”
—Carl Bernstein (b. 1944)
“Life is too short to waste
In critic peep or cynic bark,
Quarrel or reprimand:
‘Twill soon be dark;
Up, heed thine own aim, and
God speed the mark!”
—Ralph Waldo Emerson (1803–1882)
“There was such speed in her little body,
And such lightness in her footfall,
It is no wonder her brown study
Astonishes us all.”
—John Crowe Ransom (1888–1974)