Single In-line Memory modules and Dual In-line Memory Modules are basically just different ways of packaging the same silicon memory. The primary difference between these two types of modules is in the number of pins that they have. DIMMs have twice as many pins compared to comparable SIMMs. This might not seem likely at first since it is clearly visible that they have the same number of pins at each side, but closer inspection reveals that the connectors on either side are connected to each other in SIMMs. This is not the case with DIMMs.
The very apparent advantage of this is the much wider bus that a DIMM can utilize. DIMMs have a 64bit compared to the 32bit bus used by SIMMSs Wider bus means more data can pass through and this correlates to a faster overall performance since memory is essential in all computer operations. Achieving a 64bit bus is not exclusive to DIMMs since this capability has already been achieved with SIMMs via a neat little trick. The trick is to use two SIMMs in tandem, the resulting bus would be the sum of the two buses. The appearance of DIMMs have totally made this practice unnecessary.
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