Essential Information & explanations, latest texts & monographs on
Random_access_memory.
Random access memory
Random access memory or RAM is a type of computer storage whose contents can be accessed in any order. This is in contrast to sequential memory devices such as magnetic tapes, discs and drums, in which the mechanical movement of the storage medium forces the computer to access data in a fixed order. It is usually implied that RAM can be both written to and read from, in contrast to read-only memory or ROM. RAM is usually used for primary storage in computers to hold actively-used and actively-changing information, although some devices use certain types of RAM to provide long term secondary storage.
Table of contents showTocToggle("show","hide")
1 Overview
2 Common types of RAM
3 Not-so-common types of RAM
4 RAM packaging
Overview
Computers use RAM to hold the program code and data during execution. One defining characteristic of RAM is that its accesses to different memory locations are almost always completed at about the same speed, in contrast to some other technologies that required a certain delay time for a bit or byte to “come around.”
Early vacuum tube-based systems behaved much like modern RAM, even though the devices failed much more regularly. Core memory, which used wires attached to small ferrite electromagnetic cores, also had roughly equal access time (the term “core” is still used by some programmers to describe the RAM at the heart of a computer). The basic ideas behind tube and core memory are still used in modern RAM implemented with integrated circuits.
Alternative primary storage mechanisms usually involved a non-uniform delay for memory access. Delay line memory used a sequence of sound wave pulses in mercury-filled tubes to hold a series of bits. Drum memory acted much like the modern hard disk, storing data magnetically in continuous circular bands. (See primary storage for a greater discussion of these alternatives and others.)
Many types of RAM are volatile, which means that unlike some other forms of computer storage such as disk storage and tape storage, they lose their data when the computer is powered down. Modern RAM generally stores a bit of data as either a charge in a capacitor, as in dynamic RAM, or the state of a flip-flop, as in static RAM.
An interesting use of RAM is allocating parts of it as a partition, effectively acting as a hard drive, only much faster. It is usually referred to as a ramdisk.
Common types of RAM
A PC66SDRAM module
Not-so-common types of RAM
RAM packaging
Semiconductor RAM is produced as integrated circuits (ICs). RAM ICs are often assembled into plug-in modules. Some standard module types are:
- Single in-line memory module (SIMM)
- Dual in-line memory module (DIMM)
The above article is adapted from from Wikipedia All Wikipedia article text is available under the terms of the GNU Free Documentation License
Updates and comments at Essential Facts blog
World Class Photographers
Some philosophical movements
|
|
Interesting Links
Latest Dowloadable
Random_access_memory PDF s & Ebooks
Top PDF and eBook Downloads
Bibliographic Resources
Dates
20-th Century
20-th Century Details
Chromosomes and Genomics
Sports
Kitchen Knowledge
Hollywood Icons
Classical Music
Music Directory.
Music: Jazz
Music: Rock
Music: Country
Music: Popular A-E
Music: Popular F-L
Music: Popular M-S
Music: Popular T-Z
Mythology
Philosophy
Politics
Retirement
Agriculture
Agriculture: Flowers
Agriculture: Gardening
Biology
Biology & Biologists
Cell Science
Cell Science: Cells
Cell Science: Stem Cells
California
Cats & Dogs
Ethics
Electronics
Logic
The Greats
Architectural Dates & Places
Styles ABC
Styles DTOI
Styles JTON
Styles OTOZ
Buddhism
Marketing
Psychology
Enginering Systems 1
Mathematics
Classic Authors
Fear No Exams
Characters & countries
Law & Legal Topics
Linguistics
Movies
Most successful Movies
Science Plus
Science & Computers
Quantum Theory
|
