RAM 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 preceding bytes. RAM is the most common type of memory found in computers and other devices, such as printers and phones.

Types of RAM

There are different types of RAM:
  • DRAM (Dynamic Random Access Memory)
  • SRAM (Static Random Access Memory)

The two types of RAM differ in the technology they use to hold data, with DRAM being the more common type. In terms of speed, SRAM is faster. DRAM needs to be refreshed thousands of times per second while SRAM does not need to be refreshed, which is what makes it faster than DRAM.

DRAM supports access times of about 60 nanoseconds, SRAM can give access times as low as 10 nanoseconds. Despite SRAM being faster, it's not as commonly used as DRAM because it's so much more expensive. Both types of RAM are volatile, meaning that they lose their contents when the power is turned off.

RAM, Main Memory and ROM Explained

In common usage, the term RAM is synonymous with main memory, the memory available to program. For example, a computer with 8MB RAM has approximately 8 million bytes of memory that programs can use. In contrast, ROM (read-only memory) refers to special memory used to store programs that boot the computer and perform diagnostics. Most personal computers have a small amount of ROM (a few thousand bytes). In fact, both types of memory (ROM and RAM) allow random access. To be precise, therefore, RAM should be referred to as read/write RAM and ROM as read only RAM.

The RAM types on the market at the moment are:

RAM type

Pins

Width

Usage

SD RAM

168

64 bit

Older and slower type. No use.

Rambus RAM

184

16 bit

Advanced RAM. Only used for very few Pentium 4’s with certain Intel chipsets.

DDR RAM

184

64 bit

A faster version of SD RAM.
Used both for Athlon and
Pentium 4’s. 2,5 Volt.

DDR2 RAM

240

64 bit

New version of DDR RAM with higher clock frequencies. 1,8 Volt.