064 - What is Computer Memory

WHAT IS MEMORY
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A Memory or Random Access Memory (RAM) can store instructions, data and intermediate results. RAM supplies information to the other units of the computer when needed. It needs power to be read; hence, when a computer turns off, the memory is lost. For network administrators, memory is the performance lifeblood of our components.

RAM is a temporary storage area. It holds the data and instructions that the Central Processing Unit (CPU) needs. Before a program can be run, the program is loaded from some storage medium into the memory. This allows the CPU direct access to the program. Memory is a need for any computer.

The CPU calls instructions and data from the computer's memory. Because the same computer performs different tasks at different times, the memory is erasable. But there are some programs and instructions which the computer needs. It does not matter what function you are performing. These programs often are permanently recorded in the memory. So they cannot be destroyed.

The computer's memory usually consists of two parts:

Read only memory (ROM) is the permanent memory which is used to store important control programs and systems software to perform a variety of functions, such as booting up or starting up programs. ROM is non-volatile. That means the contents are not lost when the power is switched off. Its contents are written at the time of manufacture, but in modern computers may be changed using special software.

Random access memory (RAM) is used as the working memory of a computer system. It stores input data, intermediate results, programs, and other information temporarily. It can be read and/or written. It is usually volatile, that is all data will be lost when the power is turned off. In most cases it is loaded again from hard disk which is used as data storage.

Types of RAM

DRAM
• Dynamic Random Access Memory has memory cells with a paired transistor and capacitor requiring constant refreshing.

FPM DRAM
• Fast Page Mode Dynamic Random Access Memory was the original form of DRAM. It waits through the entire process of locating a bit of data by column and row and then reading the bit before it starts on the next bit. Maximum transfer rate to L2 cache is approximately 176 MBps.

EDO DRAM
• Extended Data-Out Dynamic Random Access Memory does not wait for all of the processing of the first bit before continuing to the next one. As soon as the address of the first bit is located, EDO DRAM begins looking for the next bit. It is about five percent faster than FPM. Maximum transfer rate to L2 cache is approximately 264 MBps.

SDRAM
• Synchronous Dynamic Random Access Memory takes advantage of the burst mode concept to greatly improve performance. It does this by staying on the row containing the requested bit and moving rapidly through the columns, reading each bit as it goes. The idea is that most of the time the data needed by the CPU will be in sequence. SDRAM is about five percent faster than EDO RAM. Maximum transfer rate to L2 cache is approximately 528 MBps.

DDR SDRAM
• Double data rate synchronous dynamic RAM is just like SDRAM except that is has higher bandwidth, meaning greater speed. Maximum transfer rate to L2 cache is approximately 1,064 MBps.

RDRAM
• Rambus dynamic random access memory is a radical departure from the previous DRAM architecture. Designed by Rambus, RDRAM uses a Rambus in-line memory module (RIMM), which is similar in size and pin configuration to a standard DIMM. What makes RDRAM so different is its use of a special high-speed data bus called the Rambus channel. RDRAM memory chips work in parallel to achieve a data rate of 800 MHz, or 1,600 MBps.

Note:
Having less memory chance that your computer suddenly found becomes unresponsive when lots of windows and programs open at once. Having more memory means you can run more programs at the same time without the computer slowing down.

For a basic PC, Windows XP 1GB is a good starting point and for those running Windows 7 or 8 2GB is much better or more. If you intend to use more memory intensive programs like online game or photoshop then 4GB or higher is recommended. Increasing memory make your computer much accessible.

Memory is also known as: RAM, main memory, primary memory or system memory.

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