Random Access Memory (RAM)

Computer Engineering; Information Technology

Random-access memory (RAM) is a form of memory that allows the computer to retain and quickly access program and operating system data. RAM hardware consists of an integrated circuit chip containing numerous transistors. Most RAM is dynamic, meaning it needs to be refreshed regularly, and volatile, meaning that data is not retained if the RAM loses power. However, some RAM is static or nonvolatile.

The speed and efficiency of computer processes are among the most areas of greatest concern for computer users. Computers that run slowly (lag) or stop working altogether (hang or freeze) when one or more programs are initiated are frustrating to use. Lagging or freezing is often due to insufficient computer memory, typically random-access memory (RAM). RAM is an essential computer component that takes the form of small chips. It enables computers to work faster by providing a temporary space in which to store and process data. Without RAM, this data would need to be retrieved from direct-access storage or read-only memory (ROM), which would take much longer.

Computer memory has taken different forms over the decades. Early memory technology was based on vacuum tubes and magnetic drums. Between the 1950s and the mid-1970s, a form of memory called “magnetic-core memory” was most common. Although RAM chips were first developed during the same period, they were initially unable to replace core memory because they did not yet have enough memory capacity.

A major step forward in RAM technology came in 1968, when IBM engineer Robert Dennard patented the first dynamic random-access memory (DRAM) chip. Dennard's original chip featured a memory cell consisting of a paired transistor and capacitor. The capacitor stored a single bit of binary data as an electrical charge, and the transistor read and refreshed the charge thousands of times per second. Over the following years, semiconductor companies such as Fairchild and Intel produced DRAM chips of varying capacities, with increasing numbers of memory cells per chip. Intel also introduced DRAM with three transistors per cell, but over time the need for smaller and smaller computer components made this design less practical. In the 2010s, commonly used RAM chips incorporate billions of memory cells.

Although all RAM serves the same basic purpose, there are a number of different varieties. Each type has its own unique characteristics. The RAM most often used in personal computers is a direct descendant of the DRAM invented by Dennard and popularized by companies such as Intel. DRAM is dynamic, meaning that the electrical charge in the memory cells, and thus the stored data, will fade if it is not refreshed often. A common variant of DRAM is speed-focused double data rate synchronous DRAM (DDR SDRAM), the fourth generation of which entered the market in 2014.

RAM that is not dynamic is known as static random-access memory (SRAM). SRAM chips contain many more transistors than their DRAM counterparts. They use six transistors per cell: two to control access to the cell and four to store a single bit of data. As such, they are much more costly to produce. A small amount of SRAM is often used in a computer's central processing unit (CPU), while DRAM performs the typical RAM functions.

Just as the majority of RAM is dynamic, most RAM is also volatile. Thus, the data stored in the RAM will disappear if it is no longer being supplied with electricity—for instance, if the computer in which it is installed has been turned off. Some RAM, however, can retain data even after losing power. Such RAM is known as nonvolatile random-access memory (NVRAM).

RAM works with a computer's other memory and storage components to enable the computer to run more quickly and efficiently, without lagging or freezing. Computer memory should not be confused with storage. Memory is where application data is processed and stored. Storage houses files and programs. It takes a computer longer to access program data stored in ROM or in long-term storage than to access data stored in RAM. Thus, using RAM enables a computer to retrieve data and perform requested functions faster. To improve a computer's performance, particularly when running resource-intensive programs, a user may replace its RAM with a higher-capacity chip so the computer can store more data in its temporary memory.

—Joy Crelin