A daughterboard is a circuit board in a computer that serves to enhance the current functions of a motherboard or provide it with new functions. In contrast to expansion boards, which connect to the motherboard through an electrical conductor called a bus, daughterboards generally connect directly to the motherboard. The daughterboard is sometimes referred to as a mezzanine board or daughtercard. Daughterboards are one of the most common pieces of computer hardware.

One of the major purposes of a daughterboard is to upgrade a computer. This allows the owner to avoid the expense of a new computer or major upgrade. Installing a new motherboard often improves a computer’s performance, but they are often costly. It is usually less expensive to change the daughterboards, as long as there is no need for a new Central Processing Unit (CPU) or new buses on the computer. In some computers, the CPU is located on a daughterboard.

Many older computers lack the Random Access Memory (RAM) needed to run new software. If there is not enough space on the motherboard to add more RAM, then it must typically be installed on one or more daughterboards. Older computers may also lack features common to newer computers such as an optical drive or a modem. This can be rectified with the addition of a daughterboard, allowing the user greater functionality. Since daughterboards can typically be installed fairly simply, many owners cut down on costs by doing the installation themselves.

Daughterboards are also often used to allow computers to connect to a network. Many laboratories and businesses network computers to perform tasks that often would not be possible with a single computer. Even older computers, if enough of them are properly networked, can run like a newer computer with the addition of daughterboards. Newer computers can also benefit from the enhanced functionality of a new daughterboard by allowing the user to add more capabilities later. Daughterboards are not typically found in newer desktop computers, but are commonly used in laptops.

Another function of a daughterboard is to allow customization of a computer for specialized tasks in the sciences or in development. Researchers and developers often require computer features for their work that are not commonly installed. Many companies offer daughterboards that allow the computers to be modified as needed without the expense of building a custom system. The daughterboard can be added through a connection on the motherboard.