A 72 Pin SIMM
The need for fast storage in computers has always been present. Processors process data much faster than traditional magnetic and optical medias can put out, so a faster intermediary form of storage is required. This is where RAM (random access memory) comes in. Programs are loaded to RAM, and then the processor is able to do its job much quicker, as it has a faster source from which to read and write data. As computer technology has advanced, so has the technology behind RAM.
30 Pin SIPPs/SIMMs
Some of the earliest computers, the 286s and 386s and the first Macintosh computers, used a type of RAM knows as 30 pin SIMM (Single Inline Memory Module). In the earliest 286 machines there were SIPPs (Single Inline Pin Package), SIMMs quickly took over as the pins on SIPPs were easily bent or broken, while SIMMs were constructed on PCBs (Printed Circuit Boards) with edge contacts. The data bus on SIMMs was only 8 bits wide, so for 286 and 386SX systems which were 16 bit CPUs (Central Processing Unit), SIMMs had to be installed in pairs. For 32 bit systems like the 386DX and the 486, 4 SIMMs had to be installed. 30 pin SIMMs initially came in sizes of 256KB (kilobytes), 512KB and 1MB (megabyte). Over time, they became available in 4MB, 8MB and 16MB capacities, with the 16MB variant being the largest possible 30 pin SIMM.
72 Pin SIMMs
Late model 386s, along with 486 and Pentium computers used a newer type of RAM, the 72 pin SIMM. The 72 pin SIMMs used a 32 bit bus, allowing for the use of a single 72 pin SIMM in 386 and 486 computers, or pairs in Pentiums. Some Pentium motherboards supported a "half bank" mode, allowing for the use of single 72 pin SIMMs. The 72 pin SIMMs could be had in capacities up to 128MB per stick, though 8MB and 16MB were more common, and 1MB was the minimum size.
168 Pin DIMM
DIMMs (Dual Inline Memory Modules) are the current technology. The 168 pin SDRAM (Synchronous Dynamic Random Access Memory) DIMMs are a 4th generation memory technology. They took over from 72 pin SIMMs in 1993 and proceeded to be the dominant memory type until 2000, when DDR (Double Data Rate) SDRAM took the scene. DIMMs have a 64 bit data path, and can be installed in singles since they match the processors 64 bit wide data path. DDR introduced Dual Channel technology, which garnered a speed boost from utilizing 2 DIMMs at the same time. DIMMs are the current technology choice for RAM modules, and will be for the foreseeable future. While some computers are still manufactured using standard DDR SDRAM, no computers are made with regular SDRAM anymore.
Tags: allowing single, computers used, current technology, data path, Inline Memory, SIMM SIMMs