Connecting External Devices to Your Computer: SCSI, USB, and FireWire
Many online activities — scanning photos, downloading videos or digital photos, storing back-up data — require connecting an external device to your computer.
If you look closely at your computer, you will notice different types of outlets or “ports” where peripheral devices can be plugged in.
When considering your needs, it can be helpful to understand the concept of Mbps or megabits (million bits) per second: this unit of measure indicates the rate of data transfer. The performance of external interfaces is often explained in terms of Mbps. (For example, 12 Mbps is a transfer rate of 12 million bits per second.)
Three common external connecting interfaces are:
- SCSI
- USB
- FireWire
SCSI
SCSI — small computer system interface (pronounced "scuzzy") — is the oldest of the three interface technologies mentioned on this page. SCSI is considered less stable than the more current USB and FireWire technologies.
Transfer rates with SCSI devices range from about 4 to 80 Mbps depending on the particular SCSI technology being used. Because approximately nine different SCSI technologies are in widespread use, care must be taken to use the right connectors. More about SCSI technology.
USB
USB stands for universal serial bus. Keyboards, mice, and gaming devices (like joysticks) are often plugged in via USB.
USB devices can be "hot swapped," which means they can be unplugged and plugged back in without turning the computer or the device off. More about USB technology.
FireWire
FireWire (also known as IEEE 1394, iLink, and Lynx) has a high rate of data transfer — up to 400 Mbps — and is most often used for transfer of very large files, such as with video editing. FireWire is capable of connecting 63 devices together and can also be hot swapped. FireWire also has built-in power, which means that most devices don't even need to be plugged into a power outlet. More about FireWire technology.
