Random Access Memory

From Computing Knowledgebase

RAM (Pronounced as it's Spelt), is an acronym for Random Access Memory, a type of computer memory that can be accessed randomly; that is, any byte of memory can be accessed without touching the preceeding bytes. This somewhat misleading a definition, since both RAM and ROM allow Random Access. Hence, RAM should be referred to as read/write Memory, and ROM as Read Only. In common usage, the term RAM is synonymous with 'Main Memory', the memory available to system programs, such as the Operating System.

RAM comes in many different forms, but two basic ones stand out: Volatile, and Non-Volatile. From there, two types of RAM emerge: Static RAM (SRAM) and Dynamic RAM (DRAM). The latter has speed advantages, while the former has stability advantages. RAM is the most common type of memory found in computers, and other devices, such as Printers.

The two types differ in the technology they use to hold data. DRAM needs to be refreshed thousands of times per second. Static RAM does not need to be refreshed, which makes it faster; but it is also more expensive than Dynamic RAM. Both types of RAM are Volatile, meaning that they lose their contents when the power is turned off.

DRAM is by far the most common, and is available in quite a few varieties. The earliest were called SIMMs or Single Inline Memory Modules. These were later extended to become EDO SIMMs.

The next major enhancement came in the form of DIMMs, or Dual Inline Memory Modules. If DIMMs were to be compared to SIMMs, DIMMs were essentually two SIMMs in one RAM Stick.

Early DIMMs were technically SDR or MDR. SDRAM was the most common, supplanted by DDR later on. Nowadays, however, DIMMs are referred to as DDR RAM. The next major evolutions are DDR2 and DDR3, the latter still being ratified.