The individual gold or lead connectors (pins) on SIMMs, although they are on both sides of the chip, are connected to the same memory chip, while on a DIMM, the connections on each side of the module connect to different chips. This allows for a wider data path, as more modules can be accessed at once. DIMM pins are arranged in a zigzag design to allow PCB tracks to pass between them.
The 8-byte DIMM format with dual-sided contacts can accommodate 4- and 16-megabit dynamic RAM chips, and is predicted to handle 64- and 256-Mbit devices. The 8-byte DIMM will hold up to 32 megabytes of memory using 16-Mbit DRAMs, but with the 256-Mbit future-generation DRAM, it will be able to hold a 64-Mx64 configuration. Another variation, the 72-pin SO-DIMM, is designed to connect directly to 32 bit data buses, and is intended for use in memory-expansion applications in notebook computers.
A Dual in-line memory module (DIMM), as opposed to SIMMs (used by the majority of the PC industry) allows for a 128-bit data path by interleaving memory on alternating memory access cycles. SIMMs on the other hand, have a 64-bit data path. Suppliers are unanimous in their belief that the DIMM will eventually replace the SIMM as the market's preferred memory module.