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Today's operating systems and applications are RAM hungry. When software runs out of RAM, Windows starts swapping data to and from your PC's hard disk--a much slower process than fetching it from and writing it to RAM. Adding RAM to your PC is one of the easiest and cheapest ways to boost its performance.

Just a few years ago, 16MB or 32MB of RAM were adequate for most PCs, but you need 64MB or even 128MB these days to get optimum performance with a typical set of Windows 98 applications. Plentiful RAM is even more important if you use Windows 2000 Professional. People who process images, edit video, or perform other graphics-intensive work on their PCs may need up to 384MB of RAM.

Compared to most other upgrade options, installing additional RAM is a bargain. Though prices fluctuate, the pricing trend over the past few years has been downward. At press time, RAM prices hovered at approximately $70 for 64MB, and about $125 for 128MB.

Dimming of the Day

RAM is sold in the form of chips contained on small circuit boards called memory modules. If your current desktop PC was manufactured in the last three or four years, it most likely uses 168-pin DIMMs (dual in-line memory modules). DIMMs vary depending on their capacity (16MB, 32MB, 64MB, and 128MB), the PC's bus speed, the type of RAM chips they contain, and other factors. You can usually determine what type of DIMM your PC uses by consulting the PC's manual or by calling the vendor's technical support line. Most memory vendors are happy to help (see "The Top Down"). It's important not to mix different types of memory modules in your PC.

Most PCs have three DIMM sockets on their motherboards, and one or two of them are usually free. Adding RAM is as simple as plugging in new DIMMs.

SIMMs Like Old Times

If your PC is more than three or four years old, it probably uses SIMMs (single in-line memory modules). Though the examples of memory modules shown in the photos in the accompanying steps are DIMMs, the process of upgrading SIMMs is similar. The differences are that SIMMs pivot rather than plug into their slots, and they must be installed in pairs.

Most PCs today require a type of memory called PC-100 (100-MHz) SDRAM, though slightly older systems need PC-66 (66-MHz SDRAM), and somewhat newer systems depend on PC-133 (133-MHz VC SDRAM). Some brand-new high-performance systems use a new type of memory known as RDRAM (Rambus DRAM), which currently costs considerably more than DIMMs. Another new type of memory, known as DDR (double data rate) SDRAM, is showing up in some high-speed PCs, mainly those that use AMD processors. To find out more, check out the Web sites for Rambus or Advanced Memory International.

Before You Begin

How much RAM do I have? To determine how much RAM is currently installed in your PC, watch the screen when you turn it on. Most systems check RAM at start-up and display the amount. You can also consult your system BIOS setup (details for entering it vary by PC). Or from within Windows 95 or 98, right-click My Computer and select Properties. The amount of RAM appears at the bottom of the list of system information.