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Installing new memory into your PC can be a very inexpensive way to boot the performance and reliability of your machine. Before going out and buying anything, you need to figure out what you need. If you have your system manual this job will be a lot easier. First, lets go over the different common types of memory still in usage.

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The oldest memory that any PC uses that can still run modern applications is known as DRAM. DRAM comes in two specifications, FPM (Fast Page Mode) and EDO (Extended Data Output). EDO is the newer of the two, and is faster. Both EDO and FPM DRAM come on installable circuits called SIMMS (ingle Inline Memory Modules). Now, these SIMMS (FPM or EDO) are available in two different sizes.

The older (and smaller) is known as a 30 pin SIMM, and is about 3 inches wide. A newer version is 72 pin, and about 4 inches wide. Whether the SIMMS are 30 pin or 72 pin, they both typically stand about half an inch tall. Virtually all computers that use SIMMS use non-parity SIMMS. Also, SIMMS are backwards compatible. This means you can put FPM memory in a machine designed to handle EDO, but not the other way around.

More modern computers use a type of memory called SDRAM. SDRAM actually has 168 pins, making it about 5 inches wide, and 3 quarters of an inch to a full inch tall. Of course to make things difficult for you, there are a few classifications of SDRAM also. SDRAM is classified as either PC66, PC100, and now PC133 as well. Basically, the higher the number, the faster the memory. SDRAM is backwards compatible in theory, but it is best to use the same kind already installed.

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Now that you have a basic idea of what the memory looks like, its time to find out what is in your machine. As said before, if you have the system manual this will be a lot easier… just look it up. Also, you may want to try calling your computer manufacturer, they can usually tell what type of memory you have based on the model #. If no user guide is available, you will want to shut down the system and open up the case.

If you have seen the different types of memory before, you should be able to determine whether it is 30, 72, or 168 pin memory. If you cannot tell, you should carefully remove one of the chips for inspection. For SDRAM, there is a small lever on each side of where the chip is installed. Moving the levers causes the memory to pop right out into your hand where you can read the label to find out if it is 66/100/133 SDRAM.

As for 30/72 pin SIMMS, you usually have to pull a small metal tab in the direction away from the SIMM and push the chip forward until it falls out.

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Once you know what type of memory you have, you will want to know how much memory you already have. You can check this from within Windows by going to control panel, then system, and you will see it under the general tab. You can also look at the chips. SDRAM is clearly labeled, 72 pin DRAM usually is too. Older 30 pin memory does not always say.

Next you have to figure out how much memory you want to add. IF you have a newer SDRAM system, you can just buy one chip and pop it in. Basically buy the most memory you can afford, SDRAM comes in 16MB through 256MB sizes. If all your SDRAM slots are full, you will need to replace one of the current chips.

For DRAM, things can be a little more complicated. Typically, DRAM needs to be installed in pairs, or even sets of four. If you have a 386 computer with 30 pin memory, you need to install in pairs. If you have a 486 with 30 pin memory, you need to install in sets of 4.

For 72 pin memory, on a 386 you can install the chips as singles, and in pairs on 486’s. If you look inside the case for example and see 2 filled slots and 2 open slots, then the memory is installed in pairs, and you just have to buy any 2 of the same memory type. If 4 slots are filled, you may want to try pulling out 2 chips first. If after turning the computer back on it can boot, then it just had 2 sets of 2 installed. If not, then it had a set of 4, meaning you need to replace all 4 chips with higher capacity memory.

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While all of this does sound overly complicated, for the average Pentium computer this process is extremely simple, in that virtually 90% or higher of every Pentium I/II/III/Celeron computer use PC100 SDRAM. As of June of 2000, you can walk into a Best Buy or CompUSA and walk out with a 64MB PC100 SDRAM chip for $100 and have it in an open slot within 15 minutes.