What’s the Difference Between USB and UDISK?

With all the gadgets we post about here at GetUSB.info sometimes a word or definition can get twisted on it’s meaning. One of those terms is UDISK. First, please don’t complicate the term into something more than it is. There are two answers to this question.

There is the “slang” term for UDISK and there is the “technical” term for UDISK.

The “slang” term for UDISK

The Asia / Pacific Rim region use the term UDISK to describe a flash drive. This is the most common use of the term “UDISK” for no-technical people. In the United States and Europe people do not use the term UDISK to describe a flash drive, rather the common term of “USB flash drive” or “thumb drive” or “USB key.”

The “technical” term for UDISK

The technical term for UDISK is a bridge chip which is used inside an enclosure to turn a hard drive into an external storage device that connects via USB cable.

For example, in the picture below is a hard drive enclosure which is designed to hold a magnetic hard drive and turn the hard drive into an external storage device. A magnetic hard drive typically has an IDE or SATA connection interface and a UDISK chip is used to bridge the IDE (or) SATA interface to that of USB. This bridge chip (UDISK) changes the hard from from IDE protocol (or SATA protocol) to a USB protocol.

Examine the picture a bit closer and you can clearly see the SATA interface on the PCB. On that same PCB is the UDISK bridge chip which does the protocol translation.

The second image shows the back side of the external hard drive case with the USB cable connected to the enclosure. Using the UDISK bridge chip allows for an IDE or SATA hard drive to be connected to a host computer system via USB cable.

Cypress Semiconductor (now Infineon) makes such a bridge chip, called the FX3.

Conclusion:

UDISK is most commonly used to describe a USB flash drive.

Technically the term UDISK describes a bridge chip used in hard drive enclosures.