RAM Basics

RAM in an acronym for random access memory, a type of computer memory that can be accesed 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.

There are two basic types of RAM:
  • dynamic RAM (DRAM)
  • static RAM (SRAM)

The two types differ in the technology they use to hold data, dynamic RAM being the more common type. Dynamic RAM 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. For the purposes of this article we will focus on the more commonly used DRAM.

RAM Keywords

DIMM: Dual In-Line Memory Modual, usually used to refer to the physical package RAM package.


Types of RAM

RDRAM:

Short for Rambus DRAM, a type of memory developed by Rambus, Inc. Whereas the previous memory technologies used by PCs (SDRAM) can deliver data at a maximum speed of about 100 MHz, RDRAM transfers data at up to 800 MHz. As of late 1999, Intel has been using RDRAM in its Pentium III Xeon processors and more recently in its Pentium 4 socket 423 and early socket 478 processors. RDRAM was only used for a short time and was quickly replaced my DDR.


DDR SDRAM:

DDR SDRAM ( or DDR1), or Double Data Rate Synchronous Dynamic Random Access Memory is a type of RAM

that has now been mostly superseded by DDR2, mainly because DDR2's ability to achive higher clock speeds, and requires lower voltages, then DDR1. All DDR1 DIMMs have 184 pins and has a single notch, so it cannot be inserted incorrectly into the RAM slot.
The most common speeds of DDR1 RAM are:

  • DDR-200
  • DDR-266
  • DDR-333
  • DDR-400

DDR2 SDRAM:

DDR2 SDRAM or, Double Data Rate 2 Synchronous Dynamic Random Access Memory is now the most commonly used type of RAM, in both AMD and Intel platforms. Unlike DDR1, DDR2 DIMMs have 240 pins, but they both have a single notch.

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