Do-It-Yourself Dream Machines

CPU & RAM

Let's start with the basics. Your processor and RAM are so integral to PC performance that they always make likely upgrade targets. Which is best for you?

CPU: Look Before You Leap

You want a faster PC, so you immediately think: Get a faster CPU. Think again. Though your CPU is important, PC performance depends on all your PC's components, so upgrading to a CPU that runs at twice the speed of your current processor won't come close to doubling your system's performance. A 10 to 20 percent boost is more realistic.

And you can't drop just any CPU into your motherboard; to do the job right, you'll probably have to buy an upgrade kit from Intel, Evergreen, or PowerLeap. Kits range in price from under $100 to over $400. So carefully weigh the expense versus the probable increase in speed.

Our recommendation: Don't buy a kit unless it at least doubles your current clock speed or bumps you up an entire CPU class (from Pentium II to Pentium III, say). If you're budgeting more than $250 for a new CPU, you may get a better deal by upgrading other components, or even putting the money toward the purchase of a new system.

Best Bang for Your Buck

Historically, adding memory to your PC has been the most cost-effective way to increase its performance. And with 256MB PC133 DIMMs now available for around $50, that's never been more true. If you're running Windows 98 or later, you'll see noticeable performance gains--especially while running several apps at once--if you upgrade to 128MB or more.

Fortunately, adding RAM is a fairly easy process. In fact, the hardest part of the upgrade consists of finding modules of the right type and size for your PC. For the correct RAM specifications, check the user manual or motherboard manual that came with your computer.

Most systems that people have purchased in the past several years use SDRAM, which comes in various flavors (PC66, PC100, PC133, and--on newer, often AMD, systems--DDR SDRAM). Older machines may use FPM or EDO DRAM; and some newer, pricier models use relatively expensive Rambus DRAM (RDRAM, or RIMMs).

This is usually not a mix-and-match situation; you should use the same type and speed of RAM already in your PC. Memory vendors like Crucial and Kingston offer excellent tools for matching RAM to specific PC models or motherboards.

You must also determine whether your motherboard uses SIMM or DIMM RAM modules. Most systems made in the past three years use DIMM modules, while many older PCs use SIMM modules (which are shorter and must be installed in pairs). A few PCs can take both--but often they run on only one type at a time.

Before you buy, make sure that you have the requisite open RAM slots on your motherboard and that the motherboard will accept the upgrade module you're considering. Sometimes RAM slots must be filled in a certain order or with a module of a certain capacity.

And finally, don't buy generic, budget memory. Paying a few extra dollars for DIMMs or SIMMs from a company like Kingston or Crucial can save you hours of frustration and troubleshooting.