RANDOM ACCESS MEMORY-RAM
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- Created on Wednesday, 17 February 2010 03:00
- Last Updated on Monday, 11 November 2013 10:01
- Written by Joy Joseph
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Layman's Summary: DDR 3 RAM is faster & greener than DDR2 which is faster & greener than DDR1.
RAM, acronym for Random Access Memory, so named because any part of its contents can be accessed directly or randomly. Most people know that RAM (both quality and quantity) is critical to the performance of a PC. But the terminology of RAM is confusing even to most experienced technicians. RAM is available in very many types. Today all types of RAM are integrated circuits (ICs) made of millions of transistors and capacitors. An important parameter for the RAM is its clock speed and the speed is specified in MHz.
The oldest kind of PC RAM in use today is the SD RAM. SD RAM is the acronym for synchronous dynamic random access memory. They are available in speeds (BUS frequency) of 100 Mhz and 133Mhz.
Then came the DDR SDRAM. Double Data Rate synchronous dynamic random access memory works at twice the speed of the SDRAM at the same clock speed. Thus DDR SDRAM is generally written as DDR-nnn (where nnn is the data transfer speed). DDR 266 has a memory bus clock speed of 133Mhz and transfers data at 266MHz as it has double data rate. The older SDRAM can be said to be single data rate (SDR) SDRAM. The DDR SDRAMs are available at clock speeds of 133, 166 and 200 Mhz but transferring data at 266,333 and 400 MT/s respectively.
As DDR SDRAM is superseded by the newer DDR2 SDRAM, the older DDR version is sometimes referred to as DDR1 SDRAM. DDR SDRAM modules for desktop computers, commonly called DIMMs, have 184 pins (as opposed to 168 pins on SDRAM, or 240 pins on DDR2 SDRAM), and can be differentiated from SDRAM DIMMs by the number of notches (DDR SDRAM has one, SDRAM has two). DDR SDRAM for notebook computers, SO-DIMMs, have 200 pins, which is the same number of pins as DDR2 SO-DIMMs. These two specifications, though not matching, are notched very similarly and care must be taken during insertion if unsure of a correct match. DDR SDRAM operates at a voltage of 2.5 V, compared to 3.3 V for SDRAM. This can reduce power consumption as well as heating.
DDR3 SDRAM is an improvement over its predecessor, DDR2 SDRAM, and the two are not compatible. The primary benefit of DDR3 is the ability to transfer at twice the data rate of DDR2 (at 8
