Installing or Upgrading Memory

The discussion in this section focuses on issues related to memory upgrades. In general, upgrading memory is a simple task - assuming you purchase the proper type of memory for the upgrade. Factors that affect the proper type of memory are

• Type of memory (FPM, EDO, SDRAM, DDR)
• The speed of the memory
• Pin connector type
• Parity versus non-parity

The following sections discuss each of the factors that affect how you upgrade your system's memory.

Type of memory

The first thing you need to know to upgrade your computer's memory is which type of memory you need. You first need to figure out whether you need to install a SIMM, DIMM, or SODIMM. Pentium II and later desktop computers usually need a DIMM; laptops use a SODIMM.

After you have determined the memory module type, you need to determine the type of memory to install, such as SDRAM or DDR memory.

Speed

When you buy memory, you need to take into account the speed of the memory. Older memory, such as FPM or EDO memory, is typically measured in nanoseconds (ns) and ranges from 60 ns to 80 ns. With these types of memory, it is important not to mix speeds or the system will become unreliable. The speed of a SIMM is usually indicated on the chips themselves (displaying either a numeric value or a simple minus sign with a number). For example, a memory module running at 70 ns would show either "70" or "-7" on the chips.

The speed of newer memory types, such as DIMMs and SODIMMs, is measured in MHz. If you're buying SDRAM or DDR memory, make sure you verify that you get the correct memory speed.