History of Computers - RAM

Page created by Brett Gutstein, 22 August 2011

Random Access Memory (RAM)

In general terms, RAM is a type of computer memory that can be accessed randomly, meaning that any unit of memory can be accessed without touching the preceding units. Today, RAM is the "working memory" storage area within the computer; all data is stored on the hard drive, but in order for the CPU to work with the data during normal operations, the data is read into the working memory, which is the RAM.

Overview

The earliest form of RAM is drum memory, which was invented in the 1930s. A drum formed the working memory of early machines, and programs were loaded on and off the drum with punched cards or paper tape. In the 1940s, magnetic core memory was invented. It uses the polarities of small magnetic ceramic rings to store information.

a stick of DRAM

Today, the most commonly used type of RAM is dynamic RAM (DRAM), which was first publicly released in 1970 with the Intel 1103 chip. DRAM stores each bit of data in a separate capacitor within an integrated circuit. Each capacitor can be either charged or discharged, and these two states are taken to represent 1 and 0, the two values of a bit. The charged state represents a 1 and the discharged state represents a 0. However, the capacitors in DRAM leak charge. In only a few milliseconds, a fully charged capacitor will become completely discharged unless it is refilled by the CPU or memory controller. Capacitors are like "leaky buckets" being refilled, and the refilling operation happens automatically thousands of times per second.

Significance

RAM is significant to both the history of computers and today because it is necessary for all modern computers to function. Without RAM, computers would run at excruciatingly slow speeds. Random access in RAM is over 100,000 times faster than random access in a hard drive, so if computers had to execute all programs and obtain all data from their hard drive they would be effectively unusable.