Winn L. Rosch Hardware Bible, Sixth Edition

Packaging

Most memory comes in the form of chips, individual integrated circuits meant for permanent installation on a printed circuit board. The capacity of each chip is measured in bits—or, as is more likely in the modern world, megabits. The first chips had narrow, one-bit-wide data buses, so they moved information one bit at a time. To achieve a byte-wide data bus, eight chips had to be used together (under the coordination of the memory controller). Most modern chips use wider data buses—four or eight or more bits—but none comes close to matching the 64-bit data buses of modern computers.

To make memory more convenient to install and upgrade in practical computers, memory-makers package several memory chips on a small circuit board to make ...