Computers Build It Series

The main memory on your motherboard will come in a variety of sizes and forms. These forms are SIMMs (Single Inline Memory Module) and DIMMs (Dual Inline Memory Modules). SIMMs come in 30 pin and 72 pin configurations. 30 pin memory has fallen by the wayside in popularity. They are usually only found on older systems with the slower Pentium style and slower 486 systems IT Services St. Louis. The 72 pin memory is also declining in popularity in favor of the newer DIMMs. Our recommendation is to use DIMMs whenever possible.

72 pin SIMMS are the most often used memory seen in systems today. Their sizes range from 4MBs up to the current 128MBs. They come in FPM (Fast Page Mode), EDO (Extended Data Output) and Parity SIMMs. The most often used type is EDO. These modules provide an increased performance factor over the FPM and Parity modules. Most all newer motherboard will accept EDO memory and is the recommended format of 72 pin memory. Parity memory can be used in on some motherboards. These modules provide an extra bit which is used to check the parity on the module. Although useful they are not generally used in today’s motherboards. FPM memory is the original type of 72 pin memory module. It will work in all motherboards that contain 72 pin memory slots. A safe bet if you don’t know what type of memory will work on your particular motherboard.

168 pin DIMM modules are the preferred format for use today. In many cases the motherboards seen on the market will only accept this type of memory. Pentium II motherboards are known to only accept this type of memory. There are many configurations of DIMM modules. SDRAM (Synchronous Dynamic Random Access Memory) and EDO (Extended Data Output) are the most common. These modules come in sizes ranging from 16MBs to 256MB as of this writing. They also come in buffered and unbuffered forms. Check your motherboard manual to be sure of what type memory your motherboard will support. In most cases your motherboard will support the unbuffered type. 168 pin memory also has two notches on the installation side of the module. Each notch configuration signifies a different module type such as EDO buffered and EDO unbuffered. Only one type will fit in a specific motherboard.

Another DIMM type is now in common use. It is designated as PC100 memory. This memory is designed to work on motherboards that support the 100MHz system bus speed. If you really want to make your system fast this is the type of memory you should use. Of course, it also requires the use of a motherboard that will support this speed. Super socket 7 motherboards and the BX chipset motherboards for Intel Pentium II 350MHz and up support the PC100 memory specifications. You will find the PC100 memory in 10ns, 8ns, 7ns and soon to be 6ns versions. Most motherboards recommend using 8ns or faster memory. This makes the 10ns versions of the PC100 memory obsolete already.

Installation of COM Ports

Finally we have gotten to a pretty simple set of items to install. The COM ports and printer port comprise just three items to install. We will also discuss the new USB ports while we are here. You say, “What are USB ports?” These are the newest communications ports on the market today. “USB” stands for Universal Serial Bus. The wave of the future is here today. There are not many items that support this bus as of this writing but that is changing daily. Soon you will see Monitors, Cameras, Printers and just about anything else you connect to the exterior of the computer case with the ability to take advantage of this bus. It is much faster and easier to use than the standard COMM and Printer ports. If you don’t have them yet you will with your next upgrade. They are built in to most ATX format motherboards and are available as an add-on for AT format motherboards.

Installing the COMM ports is fairly simple. Your new AT format motherboard comes with two expansion slot adapters that contain the COMM 1 and COMM 2 connectors on one adapter and the Printer Port connection on the other adapter. These can be installed directly to the back of the case in one of your available expansion slots. You may also take the ports off of the expansion slot covers and install them directly to the case in the knockout area of the case usually located closest to the power supply. In either case they will work just fine. We will first take a look at the expansion slot method.

We recommend that if you are installing the COMM ports and Printer Port in an expansion slot to locate them in the two slots closest to the power supply. This will make connection of the cables to the motherboard much easier and keep them from blocking other expansion slots. Your motherboard will also have the pins for these ports located just below these expansion slots. The easiest method to install the cables is to do it before you place the connector in the expansion slot. You will notice that the COMM port connectors have 8 pins on the cable. The motherboard has the same corresponding number of pins. On your motherboard locate the pins marked as COMM2. On your expansion slot connector locate the ribbon cable that is attached to the largest connector. This connector has 25 pins. Yes, I know. There are only 8 pins on the ribbon cable and 25 pins on the connector but that is just how it goes sometimes. Doesn’t make any sense but that is the way they make them. It just makes it easier to tell which is COMM1 and which is COMM2. Okay, look on the ribbon cable and notice that there is a red line on one side of the cable. In some cases this may be a dotted red strip. This side of the cable has the pin designated as pin 1. Find the 8 pin connector on your motherboard labeled COMM2. There should be a small “1” located on the end of the pins which designates the pin “1” location. Place the ribbon cable connector with the red stripe from COMM2 on the pins at the “1” location of the motherboard. In the same manner connect the ribbon cable connector for COMM1 to the motherboard location marked as COMM1. No you are ready to put the COMM port expansion slot cover into the case. This is pretty much self explanatory. Now your done with the COMM ports. Pretty simple wasn’t it. The next one is just as easy.

The printer port is the other expansion slot cover that came with your motherboard. The printer port connector has a ribbon cable with 26 pins. The printer port jack at the outside location of the expansion cover has 25 female pins. You will notice that this ribbon cable also has a red stripe on one side. Again this denotes the pin “1” location on the connector. On your motherboard look for the pins designated as “Printer” or maybe “PRN”. You can also check you manual for the location of the printer connector pins. Again look for the pin “1” location and connect the ribbon cable with the red stripe to the pin “1” location on the motherboard. Follow this by screwing down the expansion slot cover with the printer port jack to your case.

That’s It. You now have connected all of the COMM and Printer ports to your system. Now lets take a look at the USB port connectors. Guess what, they connect exactly like we did the COMM and Printer ports. The USB connector ribbon cable will have 18 pins. In the middle of the connector you will almost always find a closed off pin location. The motherboard will also have a pin missing in this location. This acts like a key so you can only put the connector on the motherboard in one direction. Find the location of this connector on your motherboard. It will be marked as USB or check your manual for specific locations. Attached is as we attached the ports above with the red stripe on the ribbon cable attached to the connector on your motherboard at pin “1”. Attach your ports to the exterior of the case and your done.

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