Difference between revisions of "History of Computers - RAM"
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Revision as of 17:36, 27 August 2011
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.[1]
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.[2] 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.[3] 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.[4]
Significance
References
- ↑ http://www.edgetechcorp.com/support/what-is-computer-memory.asp
- ↑ http://en.wikipedia.org/wiki/Drum_memory
- ↑ http://inventors.about.com/library/weekly/aa100898.htm
- ↑ http://www.howstuffworks.com/ram.htm