Main memory or RAM is the workspace for the computer's processor. It is a temporary storage area where the programs and data being operated on by the processor must reside.
RAM comes in the form of modules. This is basically several RAM memory chips on a small printed circuit board. These modules vary in their electrical and physical design and must be compatible with the system into which they are being installed, i.e. the motherboard's memory sockets and chipset must support the specified memory.
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When installing memory, whether you"re upgrading, repairing or building a system, you first have to determine how much memory you need. The amount of memory is measured in megabytes. The more memory you have, the more programs you can open at the same time and more memory also means that programs can be executed faster.
Memory nowadays comes in 32MB, 64MB, 128MB, 256MB, 512MB and 1GB flavours. You will also find older memory in sizes of 1, 2, 4MB, etc. When buying new memory, you will have to check your motherboard manual since different motherboards support different maximum amounts of memory. Older AT motherboards support around 16MB, Socket7 supports about 768MB and newer boards recognize about 3GB.
To know what kind of memory you need to buy or the type of memory you need to replace, you can check the motherboard manual. You can also check the memory sockets on the motherboard. The board will either have SIMM, DIMM or RIMM sockets. These are the form factors and define the shape and layout of the memory.
SIMM memory has 2 physical types, 30 pin SIMM and 72 pin SIMM. The 30 pin SIMM is about 3.5" long and usually has 8chips (8bit) or 9 chips (parity), with a straight row of connectors. The 32bit 72pin is slightly longer (4.26"), and has a notch at the bottom. Both types of memory have a cut-out at one end so they can only be installed in one direction. SIMM memory is found mainly on 486 and Pentium systems.
