A closer look at some of the internal components of a PC

Motherboard

The components inside a computer are located on a large circuit board called the motherboard. If you looked at a motherboard, you would see the CPU, main memory RAM, and connections for the other devices like the hard drive and CD-ROM drive. You would also see circuit traces connecting these components. These are the buses.

You would also see other chips soldered onto the board, resembling mini-CPUs. They might even have their own heatsink and fan. These other chips are device interfaces.

Graphics Card

The CPU does not directly generate the images that are displayed on the monitor. Instead, the images are produced by a specialized device called a graphics card or display adapter. These are small circuit boards that fit into a slot on the motherboard.

Because a video screen is constantly refreshed, the image displayed must be stored in RAM. Originally, graphics cards were just the RAM to hold the image and a device that constantly scanned through the RAM and converted the image stored there into the signals the monitor needed for display. Now, graphic cards are much more complicated.

Computers, especially those used for entertainment, have to generate incredibly complicated images and do so many times a second. Today, graphics cards are almost complete computers in miniature. They have their own large banks of specialized RAM, sometimes almost as much as main memory.

They have their own processors, which are generally more complicated, in terms of number of transistors, than the CPUs in the same system. Because these processors get very hot, they too have heatsinks and fans. Some even draw so much power that they need a special direct connection to the computer's power supply.

Sound Card

As with video, the CPU doesn't generate sound directly. Instead, the audio you hear is produced by a sound card, which is a circuit board that fits into a slot on the motherboard. Because users are often less picky about sound than video, some motherboards have the sound-producing circuits directly hardwired onto the motherboard.

The heart of a sound card is a digital-to-analog converter. This converter performs the task of modulation, which is the opposite of sampling. It takes numbers and converts them back into continuous signals. These are the signals sent to your speakers or headphones.

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