DIMMs (Dual In-line Memory Modules)
Manufacturer:	many	Speed:	6-10ns
Year Introduced:	1997	Frequency:	66-133MHz
Burst Timing:		Pins:	168/184
Voltage:	3.3-5.0v	Bandwidth:
Memory-chip modules with 168 pins that connect the modules to the PC motherboard. DIMMs are the most popular memory modules available today. They support 64-bit data transfers. As operating system Memory demands increased, larger Memory modules were required; yet the motherboard space was even more at a premium. To solve this problem the 168 pin DIMM modules ~5.375" X 1" was developed. These are installed singly in later Pentium®s, Pentium® Pro's, and PowerMacs®, and are offered as non-Parity Fast-Page, EDO, ECC, or SDRAM modes, 3.3v or 5v. buffered or unbuffered, and 2-clock or 4-clock. Their capacities are 8Mb, 16Mb, 32Mb, 64Mb and 128Mb. Choosing the right modules is very critical, as most machines require specific Types, sizes and upgrade configurations.      The number of black components on a 184-pin DIMM may vary, but they always have 92 pins on the front and 92 pins on the back for a total of 184. 184-pin DIMMs are approximately 5.375" long and 1.375" high, though the heights may vary. While 184-pin DIMMs and 168-pin DIMMs are approximately the same size, 184-pin DIMMs have only one notch within the row of pins.
Identification of 168-pin DIMM types
You can tell that a Dual In-line Memory Module is buffered if you see the buffer logic chips which are usually marked 74FCT16244 or 74ABT16244 or similar number. The no buffer DIMM does not have the buffer logic chips. Instead, the unbuffered DIMM has a small, 8-pin serial EEPROM (usually marked 24C02) which contains 128 byte module information (a lot more information compared to the simple 10 presence detect logic chips map of the buffered DIMM). ©2001, Innoventions, Inc.      All key locations are determined by their relative positioning to the center of the notch area as seen in the above diagram. The left notch determines whether the module uses a buffered or unbuffered assembly. The right notch determines the voltage requirement. Currently the 5V and 3.3V assignment are the only settings used, however, its expected that a lower settings of 1.5-2.7V will be available in the future. This new voltage requirement will take assignment on the third voltage key settings. PC SDRAM Registered DIMM Specification External dimensions: 5.375" x 1.375"

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Last Update: 10:27 PM 12/25/01