Today's computer technology has the power to simplify our lives; however, upgrading computer memory is not always simple. There are over 1,000 memory upgrade products.

How much memory do you need? Every application will dictate a minimum amount of RAM memory.

Here are some basic numbers:

Then, there are five basic different types of memory products: upgrade modules, expansion boards, SIMMs, DIMMs, and VRAMs.

An upgrade module is a small printed circuit board which holds memory upgrades for certain computers, and plugs directly into a motherboard. An upgrade module is normally made just for one specific motherboard. For example, some AST computers require special 64 pin upgrade modules with Write Per Bit memory.

An expansion board plugs into a motherboard's generic expansion slot, either PCI bus or ISA bus.

SIMMs, DIMMs, or VRAMs plug into (1) an expansion board, (2) an upgrade module, or (3) directly into the motherboard.

SIMM is the acronym for Single Inline Memory Module. This is a small printed circuit board with memory chips mounted on one or both sides. The small board has gold or “tin” plated contact pins on both sides. Pin 1 is on both front and back sides of the board. Both sides of the board for a pin make the same electrical connection. Standard SIMMs are 30 pin or 72 pin. 30 pin SIMMs are made for 8 bit data flow, typical of 286 processors. 72 pin SIMMs are designed to handle 32 bit data paths, typical of 386 and 486 processors.

DIMM stands for Dual Inline Memory Module, and gets it name because the plated pins are numbered differently from the SIMM. For example, a 72 pin DIMM has 36 pins on each side on the board: Pins 1 through 36 on the front side, and pins 37 through 72 on the back. Standard DIMMs have 72 pins, 144 pins, or 168 pins.

The 72 pin DIMM is also known as the SO DIMM, or Small Outline DIMM; it is designed for portable computers, because it is half the size of a standard 72 pin SIMM.

The CPU in a motherboard dictates the data path of a motherboard: 8 bit, 16 bit, 32 bit, or 64 bit. A 286 motherboard requires only 8 bits of data, hence a standard 30 pin SIMM is normally used. A 386SX motherboard requires 16 bits of data, thus it uses two 30 pin SIMMs at a time for memory upgrade. A 386DX or 486 requires 32 bits of data, therefore multiples of four 30 pin SIMMs or a single 72 pin SIMMs are used. A 586 or Pentium is a 64 bit beast, and the norm is to use two 72 pin SIMMs at a time or single DIMMs.

30 pin SIMMs may come with 8 bit memory without parity, or with a 9th bit for parity.

Apple computers normally use the 8 bit SIMMs, while PCs use 9 bit SIMMs.

72 pin SIMMs come with 32 bits, without parity, or 36 bits with parity. Most PCs would use 36 bit SIMMs. Newer computers can work without parity.

DIMMs are normally without parity, hence they are all 64 bits. Special computer applications still require parity, hence a special DIMM.

The fastest Pentium computers typically use either SIMMs or DIMMs. And now, the Pentim Pro or the 686 processors are beginning to arrive. Then there are dual Pentium motherboards. Does it ever stop? Not for a momemt. It goes on and on. Confusing? Yes.

Next: cache memory, EDO, SDRAM, SRAM, VRAM, etc. To be continued.

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