Introduction to Expansion Card Including Its Application [MiniTool Wiki]
What Is an Expansion Card?
What is an expansion card? The expansion card can also be called as expansion board, adapter card, or accessory card. It is a printed circuit card/board used to add other functions to the computer system via an expansion bus.
Technically speaking, all printed circuit boards plugged into the computer bus are expansion cards because they “expand” the functions of the computer. Therefore, the available expansion cards include sound cards, video graphics cards, network cards, and so on.
All expansion cards are used to enhance the quality of their specific functions. For instance, a video graphics card is used to enhance the video quality on the computer.
- In 1973, the first commercial microcomputer with an expansion slot function was MicralN. The first company to establish a de facto standard was Altair, and it developed Altair 8800 between 1974 and 1975, which later became a multi-vendor standard, namely S-100. bus.
- In 1981I, BM introduced the traceable Industry Standard Architecture (ISA) bus with the IBM PC. At that time, the technology was called the PC bus.
- In 1991, Intel introduced its PCI slot to replace ISA.
- In 1997, the AGP bus was released. The AGP bus was specially designed for video.
- In 2005, both PCI and AGP were replaced by PCI Express.
With the invention of USB, computers have become more flexible, and devices can be added to enhance performance without the need for expansion cards. However, the video card and sound card are still used to customize the PC.
The main purpose of the expansion card is to provide or expand features not provided by the motherboard. For instance, the original IBM PC did not possess onboard graphics or hard drive capabilities. In that case, the graphics card and ST-506 hard drive controller card offered graphics capability and hard drive interfaces respectively.
Some single-board computers did not provide expansion cards, and may only provide IC sockets on the board for limited changes or customization. Due to the relatively high cost of reliable multi-pin connectors, some mass-market systems (such as home computers) did not have expansion slots but use card-edge connectors on the edge of the motherboard to place expensive matching sockets into the cost of peripheral equipment.
In the case of expanding onboard capability, the motherboard can provide a single serial RS232 port or Ethernet port. Expansion cards can be installed to provide multiple RS232 ports or multiple higher bandwidth Ethernet ports. Under the circumstances, the motherboard provides basic functions, while expansion cards provide additional or enhanced ports.
The side edge of the expansion card is fixed with a contact (edge connector or pin connector) suitable for the slot. They establish electrical contact between the electronic on the card and the motherboard.
Peripheral expansion cards usually have connectors for external cables. In PC-compatible personal computers, these connectors were located in support brackets on the back of the cabinet. The connector of the industrial backplane system was installed on the top edge of the card, opposite the backplane pins.
According to the form factor of the motherboard and case, approximately one to seven expansion cards can be added to the computer system. 19 or more expansion cards can be installed in the backplane system. Total power consumption and heat dissipation become limiting factors when many expansion cards are added to the system.
Some expansion cards occupy over one slot space. For instance, as of 2010, many graphics cards on the market are dual-slot graphics cards, using the second slot as a place to place an active heat sink with a fan.
Some cards are “low-profile” cards, which means they are shorter than standard cards and can be installed in lower height computer cases. An expansion card set for external connection, such as a network, SAN, or modem card, is usually called an input/output card (or I/O card).
To sum up, this post is mainly talking about expansion card, so after reading this post, you should know its history, application as well as its physical construction.