PS / 2-SIMMs are memory modules with 72 contacts, which can be connected on one side (singlesided) or on both sides (doublesided). The memory chips can be fitted with one or both sides. Based on the memory modules used in IBM Personal System / 2 computers, the following memory modules were named “PS / 2” memories, following their origins. The PS / 2 SIMM memory modules have increasingly displaced the SIMM modules that had prevailed until around 1993 from the mainboards from 1994 onwards. Until about 1998 they were the most common types of memory modules, then they were replaced by the faster SDRAM - DIMM modules.
PS / 2 SIMMs are slightly wider than their 8-bit predecessors (see SIMM ) and have a notch in the middle of the contact strip (in addition to the recess on the edge that prevents misorientation). There are many different types of memory in the form of PS / 2 modules. The best known are FPM and EDO . The initially spread F ast p AGE M emory modules ( FPM ) were treated with the introduction of the Pentium processors by EDO (-Speicher E xtended D ata O utput ) out of the market. EDO is inMemory access around 10 to 30% faster than FPM. System-specific PS / 2 SIMMs with automatic error detection ( parity ) or even error correction (ECC, error-correcting code) were often used for use in the professional sector . These are usually specially wired and cannot be exchanged between different computer types.
Common module capacities are 4 MiB , 8 MiB, 16 MiB and 32 MiB, 64 MiB and 128 MiB are less common, although the latter does not work on all motherboards.
The later i486 motherboards have two to four slots for PS / 2 SIMMs, which can usually be equipped with any number of modules. On i586 and newer motherboards until they are replaced by SDRAM - DIMM modules, there are usually four, rarely two or six, slots for PS / 2 SIMMs. With a few exceptions, slots 0 and 1, 2 and 3 and possibly 4 and 5 must each be equipped with two modules of the same capacity.