Jim's Self-Help Memory Installation

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Static Electricity

Always use anti-static bags or foam to store an unused simm.

The risk of static discharge is a major concern when handling or installing a SIMM. Static electricity can build up within your body and discharge to the SIMM without you realizing it has happened. Combinations of cold weather, carpets, and leather soled shoes can be especially devastating. The use of anti-static devices such as wrist straps or anti-static mats is strongly encouraged. If these are not available, be sure to touch the metal back of your computer or some other grounded metal object in order to discharge yourself before handling the SIMM or other internal computer parts. Do not handle the SIMM or any other computer parts on cold dry days if you do not have an anti static device.

Anti-Static Wrist Strap

72 pin SIMM

30 pin SIMM (1 x 3)

30 pin SIMM (1 x 9)

Glossary of Memory Terminology
Check your motherboard manual to determine your exact needs.
When upgrading, try to match existing characteristics.

As opposed to DRAM and SIPPS used by older computers (XT class through some early 386), SIMM memory is utilized by today's computer generations beginning with later 386 units through the current Pentium© motherboards. Several variations exist......

30-PIN Vs 72-PIN:
As pictured above, you are limited to the physical size of SIMMS your motherboard will accept. Most 386 SIMM boards use 30-pin. 486 boards may use 30-pin or 72-pin, with some boards accepting combinations of both sizes. Pentium© boards use 72-pin exclusively.

Some older motherboards require parity memory. Most newer boards do not. Usually, parity memory can be used on non-parity boards but non-parity will not work on boards requiring parity. Mixing of parity & non-parity memory is not recommended.

Smaller numbers indicate faster speed. Most modern boards work well with 70ns or faster SIMMS. Most boards will accept faster SIMMS than they specify, however using slower memory may cause problems. Mixing speeds on the same board can sometimes be accomplished by confining all SIMMS in one bank to the same speed. To determine the speed of your existing SIMMS, check the numbers printed on the chips. 70ns is usually indicated by numbers ending in -70 or -7; 60ns by -60 or -6; etc.

The number of SIMM slots on your motherboard may or may not be divided into banks (8 slots = 2 banks of 4 slots each; 4 slots = 2 banks of 2 slots each; etc.). If the slots are banked, any bank that is used must be filled by identical SIMMS. If the board accepts combinations of 30-pin & 72-pin SIMMS, there may be limitations on which banks can be utilized in conjunction with each other. Most Pentium© boards are banked, requiring matched 72-pin SIMM pairs in each bank. If there is more than one bank on the motherboard, they are numbered beginning with zero. If you do not plan to fill all banks, bank zero should be filled first.

Extended Data Output SIMMS are a recent development allowing data to traverse a wider bandwidth than conventional SIMM memory, and are particularly effective when used in conjunction with Pentium© pipeline burst cache motherboards.


Use caution when installing or removing SIMMS. Many motherboards have plastic sockets containing small pegs that can be easily broken if the SIMM is forced.

There is a metal clamp on each end of the motherboard socket. To remove an installed SIMM, gently push these clamps away from the SIMM. If the SIMM does not release itself to a 45 degree angle, a slight push while restraining the clamps should accomplish this. The SIMM is now free and can be physically removed.

Note there is a notch on the lower end of one side of the SIMM. The motherboard socket is also notched, making it impossible to install the SIMM backwards. Also note there is a small round hold on each end of the SIMM which matches the plastic pegs on the socket.

Place the SIMM in the socket at an angle so the notch on the side of the SIMM matches the raised side of the socket.

Push the SIMM up into the socket until it locks in place. If necessary, spread the metal clamps on each side of the socket to allow proper seating.

Push down on the SIMM to ensure a good connection.

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This page last updated 09/28/11

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