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USB Nomenclature Information

There have been some recent articles and discussion about the nomenclature for the various transfer rates in the USB 2.0 standard. The USB Implementers Forum (USB-IF) regrets any confusion this may have caused. We continually work diligently with our member companies and the industry to effectively communicate this information. Please allow us to clarify this confusion.

The source of confusion derives from the fact that USB specification revision numbers and data-transfer rates are often being used in place of the logo on consumer packaging, a purpose for which they were not originally intended. The USB-IF’s recommended nomenclature for consumers is “USB” for slower speed products (1.5 Mb/s and 12Mb/s) and “Hi-Speed USB” for high-speed products (480Mb/s), as signified in the USB logos that were introduced in late 2000. In short, consumers wishing to be certain they are getting the performance they paid for in their USB products can use the logo for clarification.

The USB-IF’s naming and packaging recommendations for low- or full-speed USB products, as listed on this web site state that such products can carry only the basic version of the USB logo, which simply states “Certified USB.” We state clearly that manufacturers should avoid using terminology such as USB 2.0 Full Speed, Full Speed USB or USB 2.0. These formal recommendations were published to the USB-IF membership and posted on this web site in August 2002.

The USB-IF is a nonprofit industry organization. We do not and cannot control how manufacturers label their products. We do work continuously with system and peripheral manufacturers, striving to provide consistency in the use of this nomenclature and the logos. The logo indicates that a product’s performance against and conformance with the standard have been tested, and that the product has passed the USB-IF compliance program.

Anyone having questions about the performance of a product should contact the manufacturer for clarification.

Questions & Answers:

Q1: Why does the USB specification revision 2.0 support three data-transfer rates?

A1: The USB specification version 2.0 was created to be fully backward compatible with earlier versions of the specification for consumers’ investment protection. The USB specification revision 2.0 incorporates the higher performance that end-users requested-- the fast data-transfer rate of 480 Mb/s. By combining all three USB data transfer rates into the latest specification, peripherals already running at the slower speeds (1.5 Mb/s, 12 Mb/s) covered by earlier versions of the specification (1.0 and 1.1) are designed to be fully compatible with other products designed to the USB specification version 2.0. So this way, you plug it in – and it just works.

All USB 2.0-compliant systems, such as laptop, notebook, and desktop computers, must by definition support all three data rates: 1.5 Mb/s, 12 Mb/s, and 480 Mb/s. The nature of peripherals, however, creates a situation that is a little less clear. One class of peripherals may be available with either the fast data-transfer rate of 480 Mb/s or the slower data-transfer rate of 12 Mb/s. Included are:

digital cameras
CD-ROM burners
DVD drives
motherboards
flash card readers
adapter cards
scanners
other products

The second class of peripherals operates at slower speeds because these peripherals do not need fast data-transfer rates. (And if they supported such performance, it would add considerably to their cost to the consumer.) These include:

joysticks
keyboards
mice
other products

They operate at the two lower data-transfer rates of either 1.5 Mb/s or 12 Mb/s.

Q2: As a consumer, what should I look for when I want to purchase a product that runs at the fastest speed possible?

A2: Look for the Certified Hi-Speed USB Logo.

This logo indicates that a product has successfully completed the USB-IF Compliance Testing Program and supports the Hi-Speed USB data transfer rate of 480 Mb/s. Products that can take advantage of the faster data transfer rates of Hi-Speed USB include products such as CD-RWs, DVD drives, flash card readers, digital cameras and scanners.

For products that do not require the higher data transfer speeds of Hi-Speed USB, look for the Certified USB Logo.

This logo indicates that the product has successfully completed the USB-IF Compliance Testing Program for products operating at original USB speeds (1.5 Mb/s or 12 Mb/s).

Q3: As a product designer, what should I look for when I create a new product based on the USB specification – and I want it to run at the fastest speed possible?

A3: Designers of USB products should use only the USB 2.0 specification as their guide. This specification describes the physical features, a full range of performance characteristics and other matters for all USB product designs. All earlier versions of the specification are obsolete.

Q4: Why don’t all USB products operate at the fastest speed, i.e. Hi-Speed USB?

A4: For a keyboard, joystick or mouse, increased speeds add no benefit to performance. For other products, such as digital cameras, peripheral performance is better at faster speeds.

Q5: What should I do if I see packaging that is unclear regarding USB speeds?

A5: If product packaging is unclear, please contact the manufacturer of the product you plan to purchase and ask for clarification on the speeds it is designed to support.