What is the difference between memory with 2DIMMs vs 4DIMMs?

First off I don't really know what DIMM means and what it does. Would there be any marked difference in system performance based on whether you have 2DIMM or 4DIMM memory and therefore would it be worth paying the extra money for 4DIMMs? Any suggestions would be greatly appreciated.

Thanks,
MJ

 

A DIMM, or dual in-line memory module comprises a series of random access memory integrated circuits. These modules are mounted on a printed circuit board and designed for use in personal computers. DIMMs began to replace SIMMs (single in-line memory modules) as the predominant type of memory module as Intel's Pentium processors began to control the market.

The main difference between SIMMs and DIMMs is that SIMMs have a 32-bit data path, while DIMMs have a 64-bit data path. Since Intel's Pentium has (as do several other processors) a 64-bit bus width, it required SIMMs installed in matched pairs in order to use them. The processor would then access the two SIMMs simultaneously. DIMMs were introduced to eliminate this inefficiency. Another difference is that DIMMs have separate electrical contacts on each side of the module, while the contacts on SIMMs on both sides are redundant.

The most common types of DIMMs are:
72-pin-DIMMs, used for SO-DIMM
144-pin-DIMMs, used for SO-DIMM
200-pin-DIMMs, used for SO-DIMM
168-pin-DIMMs, used for FPM, EDO and SDRAM
184-pin-DIMMs, used for DDR SDRAM
240-pin-DIMMs, used for DDR2 SDRAM

http://img166.imageshack.us/img166/4707/dimmsob8.jpg

The way I understand it each memory slot has its own channel, so if you have two memory slots you have two channels, four, four/quad channels. On DDR2 each channel gets two cycles per clock cycle, so in theory 4x512 DIMM would be the same speed as 2x1Gb DIMM if the memory was the same frequency, however the price would be higher, but you could also upgrade to 4x1Gb without chucking Dimms.

OH and welcome to Major Geeks