computer ram

RAM (random access memory) is the place in a computer where the operating system, application programs, and data in current use are kept so that they can be quickly reached by the computer's processor. RAM is much faster to read from and write to than the other kinds of storage in a computer, the hard disk, floppy disk, and CD-ROM. However, the data in RAM stays there only as long as your computer is running. When you turn the computer off, RAM loses its data. When you turn your computer on again, your operating system and other files are once again loaded into RAM, usually from your hard disk.

RAM can be compared to a person's short-term memory and the hard disk to the long-term memory. The short-term memory focuses on work at hand, but can only keep so many facts in view at one time. If short-term memory fills up, your brain sometimes is able to refresh it from facts stored in long-term memory. A computer also works this way. If RAM fills up, the processor needs to continually go to the hard disk to overlay old data in RAM with new, slowing down the computer's operation. Unlike the hard disk which can become completely full of data so that it won't accept any more, RAM never runs out of memory. It keeps operating, but much more slowly than you may want it to.

RAM is small, both in physical size (it's stored in microchips) and in the amount of data it can hold. It's much smaller than your hard disk. A typical computer may come with 1 to 2 Gigabytes of RAM compared to a hard disk that can hold 80 to 500 (or more) Gigabytes (depending on your needs).

Most personal computers are designed to allow you to add additional RAM modules up to a certain limit. Having more RAM in your computer reduces the number of times that the computer processor has to read data in from your hard disk, an operation that takes much longer than reading data from RAM.

In addition to disk, floppy disk, and CD-ROM storage, another important form of storage is read-only memory (ROM), a more expensive kind of memory that retains data even when the computer is turned off. Every computer comes with a small amount of ROM that holds just enough programming so that the operating system can be loaded into RAM each time the computer is turned on.

When updgrading memory, it is essential that you purchase the right type of memory module, because DDR, DDR2, and DDR3 memory is incompatible with each other. You cannot use a DDR2 module in a DDR DIMM slot, etc.

Most DDR/DDR2/DDR3 memory comes in matched pairs of modules to take advantage of dual-channel mode. Modern motherboards have a dual-channel memory bus, which makes it possible for pairs of modules to have a performance advantage compared to using a single of the same size. In other words, two 1GB modules in dual-channel mode outperform a single 2GB module that can only operate in single-channel mode.

A computer running Windows XP Home Edition that doesn't run memory-hungry applications, such as video-editing software, should have minimum of 512MB of RAM memory to run comfortably. Such a computer will run ordinary office applications, etc., with 256MB of memory, but slowly. Motherboard user manuals recommend that the 32-bit versions of Windows XP Home and Professional Editions should have less than 3GB of memory installed, because they don't support more than that amount of memory. The 64-bit version of Windows XP Professional supports a maximum of 8GB of memory.

Can you mix and match ?     No!

When adding additional memory, you need to match the RAM that is already in the system.