RAM doesn’t bite. RAM is where information is stored before being sent to the CPU for processing, and where it is stored after being processed by the CPU. These days, RAM comes in two different types of memory module –single inline memory modules, or SIMMs, and dual inline memory modules, or DIMMs. The older of the two types are the 72-pin SIMMs. Most machines use 168-pin DIMMs instead these days. Pentium and higher processors require a data width of 64 bits, but SIMMs are restricted to 32 bits and therefore must always be installed in pairs in Pentium and higher systems. DIMMs have the required data bus width of 64 bits and can be installed as single modules without problems. Installing DIMMs is also easier than installing SIMMs, because the former can be inserted directly while the latter have to be inserted at an angle and then pivoted into position.

Another difference is that SIMMs require 5V while DIMMs (which also used to run at 5V) now require only 3.3V. A new type of DIMM called PC100 DIMMs were introduced to support the 100MHz bus speed standard. DIMMs and 72-pin SIMMs are available in 8, 16, 32, 64, 128 or 256MB sizes, though not all motherboards supports the last type.

The two types of RAM currently being used by most users are EDO (extended data out) RAM and SDRAM (synchronous dynamic RAM). The former type is the older one, and is used in SIMMs as well as DIMMs. SDRAM is the newer type and is correspondingly used only in DIMMs. In general, mixing SIMMs and DIMMs, or EDO RAM and SDRAM, is not recommended. Today, we’ll be talking about the more up-to-date type: SDRAM. But before we get to the actual memory modules under review, there are a few points to be covered- what is it that you should look for in memory? And what do some of those strange acronyms mean?