Computer Memory Upgrade
Your guide to computer memory upgrades,
RAM buying guide, and guide to install compatible RAM.

Table of Contents

How computer RAM works?

Similar to a microprocessor, a memory chip is an integrated circuit (IC) made of millions of transistors and capacitors. In the most common form of computer memory, dynamic random access memory (DRAM), a transistor and a capacitor are paired to create a memory cell, which represents a single bit of data. The capacitor holds the bit of information -- a 0 or a 1. The transistor acts as a switch that lets the control circuitry on the memory chip read the capacitor or change its state.

RAM stands for Random Access Memory. This means Information can be retrieve and store by the computer at any order. RAM gives your computer a temporary place to process electronic data. This means that, RAM chips continue to store information only as long as computer has electrical power. In other words, when you shut off your computer, all the data stored in RAM are lost.
All actual computing starts with the the CPU (Central Processing Unit).

The chipset supports the CPU and contains several controllers that control how information travels between the CPU and other components in the PC.

The memory controller is part of the chipset and establishes the information flow between memory and the CPU.

A bus is a data path that consists of parallel wires and connects the CPU, memory and other devices. The bus architecture determines how much and how fast data can move around the motherboard.

The memory bus goes from the memory controller to the computer's memory sockets. Newer systems have a frontside bus (FSB) from the CPU to main memory and a backside bus (BSB) from the memory controller to L2 cache.

For the PC to get information...

The CPU sends a request to the memory controller to memory and gets a report back of when the information will be available. This cycle can vary in length according to memory speed as well as other factors, such as bus speed.

Residing on the motherboard, the system clock sends a signal to all components, just like a metronome ticking. Each click of the clock represents a clock cycle. A clock running at 100Mhz represents 100 million clock cycles per second. Every action is timed by the clock where different actions require a different number of clock cycles.

Many people assume that the speed of the processor is the speed of the computer. Most of the time, the system bus and other components run at different speeds. Because all information processed by the CPU is written or read from memory, the performance of a system is dramatically affected by how fast information can travel between the CPU and memory. Therefore, faster memory technology contributes greatly to the overall system performance.

Cache memory is a relatively small amount (normally less than 1 MB) of high speed memory and resides very close to the CPU. It is designed to supply the CPU with the most frequently requested data. It takes a fraction of the time, compared to normal memory, to access cache memory.

The concept is that 20% of the time, what is needed is in cache. The cache memory tracks instructions, putting the most frequent used instruction at the top of the list. Once the cache is full, the lowest need is dropped.

Today, most cache memory is incorporated in the CPU. It can also be located just outside of the CPU. Cache that is closest to the CPU is labeled Level 1, the next closest Lever 2, etc.

Interleaving is a process in which the CPU alternates between two or more memory banks. Every time the CPU addresses a memory bank, the bank needs about one clock cycle to reset. The CPU can save processing time by addressing a second bank while the first bank is resetting.

Check this site for  information about DDR SDRAM memory and DDR Memory recommendations.

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 2003  Computer Memory Upgrade