A dual in-line memory module (DIMM) consists on a series of dynamic random-access memoryintegrated circuits. These modules are placed on a circuit board which is specifically designed for use in workstations, personal computers and servers. Now days DIMM ddr memory had replaced SIMMs (single in-line memory modules) as a dominant type of memory modules. DIMMs have separate electrical contacts on each module, while SIMMs have same contents on each side of module this is the key reason which differentiates it from SIMMs.
DIMM ddr memory came in different types these are 72 pin SO-DIMM, 100-pin DIMM, 144-pin SO-DIMM, 168-pin DIMM, 172-PIN Micro-DIMM which is used for DDR SDRAM,184-pin DIMM which is used for DDR SDRAM and so on. However DDR DIMMs also came in different types which are DDR, DDR2 and DDR3 these all have different number of pins in it and these pins are located at different notch positions.Different technologies have different bus and device clock frequencies that are set as standard for them. There are also set standards for each of the type. Like SDR DIMMs were the first synchronous registered DRAM DIMMs which works with the same bus frequency for data, address and control lines.
For the first type of DDR DIMMs named as DDR1 DIMMs, they based on Double Data Rate (DDR) DRAM. In this type they had doubled the data rate but the strobe of the clock rate remains the same. This mechanism of doubling the data rate was achieved by clocking on both the rising and falling edge of the data strobes. In second type of DDR DIMMs named as DDR2 DIMMs they works on the mechanism of Double Data Rate2 (DDR2) DRAM with double data rate and double strobe frequencies rate for clock. It was also achieved by the clocking on rising and falling edges of data strobes. DDR2 provides the same speed with lower power consumption as compared to the DDR1. In third type of DDR DIMMs named as DDR3, they work on the mechanism of Double Data Rate 3 (DDR3) DRAM which have double data rate and strobe frequencies rate of clock. This can be achieved similarly as DDR1 and DDR2 by rising and falling edges of the data strobes. DDR3 provides higher speed at lower power consumption in comparison to DDR1 and DDR2.
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DIMMs commonly use several form factors. Single Data Rate (SDR) SDRAM DIMMs commonly came in two categories of heights: 1.7-inch and 1.5-inch. When rack mount servers were introduced then the concept of separate plugin into the angled DIMM sockets was also introduced to fit in their 1.7 high ports. After this a new concept of DDR DIMMs were introduced, where we have to plugin in a less high port of 1.2 heights. When blade servers were introduced the plugin concept remains same but the only changes was coming with the passage of time was the reduction in the height of port now it was introduced as 0.72, which was named as the development of Very Low Profile (VLP). After this DIMM form factors include the SO-DIMM, the Mini-DIMM and the VLP Mini-DIMM.