IV RAM Packaging
The way in which RAM is organized both physically and logically in a PC is referred to as RAM Packaging. The best way to understand how RAM is organized is to view it in a hierarchal structure. At the bottom of the hierarchy is a memory cell. This is an area of memory made up of bits that can hold a series of 1s or 0s. The number of bits that make up a cell is expressed by the bit width of the memory. The cell is the smallest unit of memory that the system can read from or write to.
Moving up the hierarchy, we have memory chips. These chips are typically made of ceramic or plastic, and have a row of pins one each side. Chips are made up of cells. The number of cells on a memory chip, multiplied by the bit width of the cells will give you the storage capacity of the chip. In older PCs, these chips where installed directly onto the motherboard.
On the next level of the memory hierarchy is the module. A module contains multiple chips soldered to a small epoxy circuit board. The entire module fits into a socket on the motherboard.
Finally, at the top of the hierarchy, memory modules are grouped into banks. The width of the system data bus compared to the width of the modules data bus will determine the number of modules needed to make up a bank. For example, a Pentium class system has a 64-bit data bus. If we were to use 32-bit wide modules, we would need two modules of matching size and speed to make a bank. The system cannot access portions of a bank.
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