Random Access Memory

RAM consists of computer chips, which store information. It is the form of volatile memory used to hold temporary instructions and data for manipulation while the system is running. . The term random is applied because the CPU can access or place data to and from any addressable RAM on the system. If power to the system is lost, all RAM is lost as well. They are installed in rows called banks of nine on the motherboard. Only 8 chips per row are used to store data while the 9th is used for parity checking. Data transfer between the CPU and RAM occurs at the fastest possible rate since it involves no moving parts as do hard and floppy disk drives. RAM is memory that your computer uses to run programs and software applications on your computer. Without RAM your computer won't function. The more RAM you have the faster and more smoothly your computer will run. This memory is searched if the data can’t be found I L1 or L2 cache memories. There are now different types of RAM chips available. These include:

SIMM 30-pin (usually FPRAM ) - SIMMs (single inline memory modules) quickly replaced SIPPs because they are easier to install. They are similar to SIPPs with one exception—they require no pins; 30-pin SIMMs have 30 contacts in a single row along the lower edge . A 30-pin SIMM can have as few as two or as many as nine individual DRAM chips. Although SIMM modules can have pin counts as high as 200, in PCs, 30- and 72-pin versions are the most common.

SIPP (usually FPRAM) -One of the first module forms of DRAM, the SIPP (single inline pinned package) is a printed circuit board with individual DRAM chips mounted on it. Physically, a SIPP module looks like a rectangular card with a single row of pins along one edge. The SIPP had a very short time in the sun due to the fragile nature of these pins.

SIMM 72-pin (so-called "PS/2 SIMM", usually EDO RAM ) -With the advent of 32- and 64-bit CPUs, the bank began to take up too much space on the motherboard and added to the cost of memory. (The board that houses the chips often costs more than the DRAM chips.) Enter 72-pin SIMMs, with 72 pins on each card. One of these is four times wider than a 30-pin SIMM, which is 8 bits wide. Therefore, a motherboard requiring four rows of 30-pin SIMMs to fill one bank needs only one 72-pin SIMM. Virtually all Pentium and Pentium Pro systems use 72-pin SIMMs. Because 72-pin SIMMs is 32 bits wide, the term x 32 is used to describe them. A 1 MB × 32 SIMM contains 4 MB of RAM because it is 4 bytes wide (1 MB of RAM is 1,048,576 × 32, which equals 4 MB). Remember, memory is measured in bytes, and chips are measured in bits.

-SIMMs usually require matched pairs to form a bank of memory

Note Bank= It is used to describe the necessary rows of chips, as well as the slots into which they are inserted

DIP 16-pin (RAM chip, usually pre-FPRAM )

-DIP (dual inline package) = this was soldered right onto the motherboard, but most often it was seated in a socket, offering a simpler method of removal and replacement. Some older machines have special memory expansion cards that contain several rows of sockets. These cards are placed in a slot on the motherboard. To upgrade or add memory, new chips had to be individually installed on the motherboard (eight or nine chips per row—nine chips if using parity). This could be challenging, because each chip had 16 wires that needed to be perfectly aligned before insertion into the base. The notch in one end denoted the side that had pin 1.

DIMM

- DIMMS (dual inline memory modules)

-DIMMS are a real improvement over older memory modules. They provide larger amounts of RAM on a single module and are easy to install. They slide straight down into a slot and are secured by a pair of locks that swing into place above the card as it seats fully in the slot.

· DIMM 168-pin (SDRAM)

· DIMM 184-pin (DDR SDRAM