PCMCIA Card Vs. USB
Computer peripherals, such as printers, scanners, storage devices and multimedia devices, connect to computers through external interfaces commonly referred to as plugs, sockets or slots. Two common interfaces are PCMCIA slots and USB plugs. Attaching a peripheral device to a computer through either type of interface allows the computer to communicate with the device, thereby extending the computer's capabilities. PCMCIA devices and USB devices share common characteristics and are used for common purposes but also differ in a number of respects.
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PCMCIA
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The PCMCIA, or Personal Computer Memory Card International Association, creates and publishes standards for PC Cards. The physical standard for PC Cards requires a 68-pin interface between the PC Card and the computer's card slot. PC Cards come in at east three different form factors, referred to as Type I, Type II and Type III, which vary in their relative thickness. Additional types of cards, such as the proposed Type IV card developed by Toshiba, comply with some or all of the established PCMCIA standards but are not officially recognized by the PCMCIA.
USB
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The USB, or universal serial bus, standard is published by the USB Implementers Forum, a non-profit organization founded by a group of leading technology vendors. USB sockets can, as the name implies, be connected serially, so that multiple devices can be plugged into a single USB socket on a computer. Additionally, USB sockets provide both communication between a peripheral device and a computer and power flow from the computer to the peripheral device. In cases where a USB device's power requirements exceed the capacity of the USB socket, USB devices may also use external power sources.
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Applications
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PCMCIA and USB technologies enable a wide range of peripheral computer technologies. For example, both enable multimedia hardware, such as webcams and speakers, security-oriented hardware such as biometric scanning devices and remote-access technologies, such as Bluetooth connections. Similarly, both have implementations that allow computers to connect to networks and to the Internet, through Ethernet, wireless and cellular connections. And, both enable additional storage for computers, with PCMCIA devices typically providing the storage device internally and USB devices providing the storage through externally.
Similarities
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Both PCMCIA and USB technologies were originally driven by the goal of finding ways to connect devices to computers without requiring that the computer be opened. The general approach behind both PCMCIA and USB technologies has been to create standards for technology interoperability. Both standards, to that end, define their technologies' respective requirements in terms of physical dimensions, electromechanical characteristics and software interactivity. And, both standards are widely implemented and have been used for a variety of applications.
Differences
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PCMCIA standards are intended to promote the use of self-contained, small form-factor cards to enable peripheral computer technologies. USB standards are intended to allow computer peripherals of any shape or size to connect to a single, standardized computer socket. As a result, PCMCIA technologies are often focused on enabling peripherals where size is crucial, such as in the case of mobile computing, while USB has no similar focus. Moreover, the PCMCIA continues to refine its existing published standards and to introduce new standards, such as those for the CardBus and ExpressCard standards, while the USB 2.0 standard has remained unchanged despite the release of a USB 3.0 standard in 2008.
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