Memory is available in various physical packaging. Roughly in order of their appearance, the major types of DRAM packaging include the following.
This package comprises a rectangular chip with a row of pins down each long side, making it resemble an insect. DIP was the most common DRAM package used in PCs through early 386 models. DIP chips were produced in Page Mode and Fast Page Mode, and are long obsolete. DIP packaging was also used for L2 cache memory on most 486 and some Pentium-class motherboards. DIP DRAM is useless nowadays.
This package turns a DIP chip on its side and extends all leads straight out one side parallel to the plane of the chip. SIPPs were intended to allow memory to be installed more densely, and were used in a few 386SX systems, but never caught on. SIPPs were produced in Page Mode and Fast Page Mode form, and are long obsolete.
This package mounts multiple individual DRAM DIP chips on a small circuit board with a card edge connector designed to fit a socket on the motherboard. Mainstream SIMMs have been manufactured in two form factors:
These SIMMs were used in a few 286 systems, most 386 systems, and some 486 systems, and were produced in Page Mode and Fast Page Mode form. Although they are still available, 30-pin SIMMs are obsolete. If you tear down an old system, any 30-pin SIMMs you salvage are too small and too slow to be useful ...