COMPUTER MEMORY AND TYPES OF MEMORY MODULES

COMPUTER MEMORY AND TYPES OF MEMORY MODULESFATHIMA THENSILA .CNO:- 13

COMPUTER MEMORYMemory is the most essential part of a computer.Without memory there would be no computer, as we know it today.It is used for storing both instructions to be executed and data.The CPU accesses each location in memory by using a unique number, called a memory address

COMPUTER SYSTEM COMPONENTSCentral Processing Unit

OutputDevices

CacheMemory

Primary Storage

SecondaryStorageDevicesControlUnitALU

SpecialPurposeProcessors

Output Devices

InputDevices

TYPES OF MEMORY PRIMARY MEMORY OR MAIN MEMORY

Random Access Memory (RAM)Read Only Memory (ROM)

CACHE MEMORY

Level 1 (L1) cacheLevel 2 (L2) cache

III. SECONDARY MEMORY

Optical Media DevicesMagnetic Media Devices

PRIMARY MEMORY OR MAIN MEMORYDirectly or indirectly connected to the CPU via amemory bus.

Comprises of two buses: an address busand a data bus

The CPU firstly sends a number through an address bus, a number called memory address, that indicates the desired location of data. Then it reads or writes the data itself using the data bus.

Additionally, A Memory Management Unit (MMU) is a small device between CPU and RAM recalculating the actual memory address, for example to provide an abstraction of virtual memoryor other task.

CONTINUEDBroadly, the main memory is of two types-

i. Random Access Memory (RAM) ii. Read Only Memory (ROM).

MEMORY ADDRESSESMemory is a collection of cells, each with a unique physical/memory address Each cell can hold one byte or 8 bits

STORAGE CAPACITY

RANDOM ACCESS MEMORYA RAM memory chip is an integrated circuit (IC) made of millions of transistors and capacitors. RAM is volatile (temporary). Programs and data can be written to and erased from RAM as needed. This means that RAM does not retain its bit configuration when the power is turned off.

CONTINUEDThis is a type of memory serves asMain Memory Of A Computer.

It temporarily stores copy of information and files loaded from a computer hard drive that are required by a processor.

RAM stores data randomly and the processor accesses these data randomly from the RAM storage

TYPES OF RAMThere are two different types of RAM:DRAM (Dynamic Random Access Memory)SRAM (Static Random Access Memory).

The two types of RAM differ in the technology they use to hold data, with DRAM being the more common type.

DRAM(DYNAMIC RAM)Dynamic random-access memory (DRAM) is a type of random-access memory that stores each bit of data in a separate capacitor within an integrated circuit.

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TYPES OF DRAMDRAM chips are available in various designs:EDODRAM (Extended Data Out DRAM)SDRAM (Synchronous DRAM)RDRAM (Rambus DRAM)DDRDRAM (Double Data Rate DRAM)

SRAM(STATIC RAM)SRAM is a type of memory that is faster and more reliable than the more common DRAM (dynamic RAM). The term static is derived from the fact that it doesn't need to be refreshed like dynamic RAM.

TYPES OF SRAMDifferent types of SRAM are:Asynchronous SRAMsSynchronous SRAMsSpecial SRAMsNon-Volatile RAM (NVRAM) and Battery-Back SRAM (BRAM)

DIFFERENCE BETWEEN DRAM AND SRAM

READ ONLY MEMORY(ROM)It performs only read function not write function. So the data stored in ROM cannot be modified.ROM is non-volatile

TYPES OF ROM PROM: programmable ROMOnly written once EPROM: erasable PROMUse ultraviolet light to erase data EEPROM: electronically EPROMCan be erased using electronic impulses (higher voltages)

CACHE MEMORYIt is a high speed storage mechanism

It Can be either a reserved section of main memory or an independent storage device.

It speeds up access to data and instructions stored in RAM.

CONTINUEDMEMORY CACHE:-It is a portion of memory of SRAM instead of the slower DRAM. By keeping as much of the information as possible in high speed SRAM, it avoids accessing the slower DRAM.DISK CACHE:-It works under the same principle, but uses conventional main memory (DRAM) instead of high speed SRAM. It improves the computers performance a lot as accessing data from RAM is much faster than from hard-disk.

TYPES OF CACHE MEMORYLevel 1 (L1) cacheBuilt inside the CPU.It works at half CPU clock speed.Level 2 (L2) cacheBuilt external to CPU, in the motherboard.It works at the motherboard bus speed

Nowadays both L1 and L2 are integrated in the CPU to reduce access time and further improve system performance.

MEMORY CACHE

DISK CACHE

SECONDARY MEMORYStorage devices hold data, even when the computer is turned off.The physical material that actually holds data is called a storage medium. The surface of a floppy disk is a storage medium.The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device.The two primary storage technologies are magnetic and optical.

MAGNETIC STORAGE DEVICEMagnetic storage uses different patterns ofmagnetizationin a magnetizable material to store data.It is a form ofnon-volatile memory. The information is accessed using one or moreread/write heads. HARD DISKS and FLOPPY DISKS are such devices.

HARD DISKSIt stores information on one or more continuously spinning disks which are coated with magnetic material.

CONTINUEDInformation is recorded by magnetic heads called access arms.

These days, hard disks have storage capacity between 80 to 300 GB.

FLOPPY DISK(DISKETTE)It is made of a flexible substance called Mylar.

It has a magnetic surface for recording data.

It stores up to 1.44 MB of data.

CONTINUEDIt cannot include graphics or pictures within it.

All floppy disks must be formatted before data can be written on it.

OPTICAL STORAGE DEVICEThese are generally circular disc which can containdataencoded in bumps on a special material on one of its flat surfaces. The encoding pattern follows a continuous, spiral path covering the entire disc surface and extending from the innermost track to the outermost track.

CONTINUED..The data is stored on the disc with alaseror stamping machine, and can be accessed when the data path is illuminated with alaser diodein anoptical disc drive

Optical storage devices are mainly two types:CDDVD

COMPACT DISK

CDs are very cheap and store up to 700MB of data.

They are of three types:-

CD-ROM (CD Read Only Memory)CD-R (CD Recordable)CD-RW (CD Rewritable

DIGITAL VIDEO DISK(DVD)It is of the same size as a CD but stores 15 times as much information, is 20 times faster than it.

It can hold 17 GB of data.

CONTINUEDIt comes in three varieties:-DVD-ROM (DVD Read Only Memory)DVD-R (DVD Recordable)DVD-RW (DVD Rewritable)

NEW AGE MEMORY DEVICES FLASH MEMORY Is anon-volatilememory It is a specific type ofEEPROM Primarily used inmemory cardsandUSB flash drive

CONTINUED BLU-RAY DISKSupersedes DVDsUses blue-violet laserto read the discstores almost six times more data than on a DVD

TYPES OF MEMORY MODULESDifferent types of memory modules are:-DIMM(DUAL IN-LINE MEMORY MODULE)SO-DIMM(Small outline DIMM)M-DIMM(MICRO DIMM)SIMM(SINGLE IN-LINE MEMORY MODULE)RIMM(RAMBUS IN-LINE MEMORY MODULE)

SIMM(SINGLE IN-LINE MEMORY MODULE)SIMM stands for Single In-Line Memory Module.

A SIMM consist of memory chips soldered onto a modular printed circuit board (PCB), which inserts into a socket on the motherboard.

72 pin SIMMs transfer 32 bits of data at a time, therefore in modern microcomputers with a 64-bit data bus two SIMMs have to be paired up in order to function.

CONTINUED30 pin SIMM - 1st gen. of SIMM (286,386 CPU 8 & 9 bit parity configuration)

DIMM(DUAL IN-LINE MEMORY MODULES)Dual In-line Memory Modules, or DIMMs, closely resemble SIMMs.DIMMs install vertically into expansion sockets. The difference between the two is that on a SIMM, pins on opposite sides of the board are "tied together" to form one electrical contact; on a DIMM, opposing pins remain electrically isolated to form two separate contacts.

DIMMSingle-sided DIMMMemory chips installed on one side of moduleDouble-sided DIMMMemory chips installed on both sides of moduleMemory bankMemory processor addresses at one time.64 bits wideDIMMs can always be installed as single DIMMs on a motherboard

DIMM168 Pin DIMM72 Pin SODIMM:- Used in p2 Laptop computer.144 Pin SODIMM:- Found in Laptop.100 Pin DIMM:- Used in Printers.100 Pin RIMM184 Pin DIMM:- Used on MotherBoards.200 Pin SODIMM

DIMM168-pin DIMMs transfer 64 bits of data at a time and are typically used in computer configurations that support a 64-bit or wider memory bus.

SO-DIMMA type of memory commonly used in notebook computers is called SO DIMM or Small Outline DIMM. The principal difference between a SO DIMM and a DIMM is that the SO DIMM, because it is intended for use in notebook computers, is significantly smaller than the standard DIMM.

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SO-DIMMThe 72-pin SO DIMM is 32 bits wide and the 144-pin SO DIMM is 64 bits wide.

72-Pin SO-DIMM144-pin SO-DIMM

RIMM(RAMBUS IN-LINE MEMORY MODULE)These are 64-bit memories developed by Rambus.RIMMs look similar to DIMMs, but have a different pin count. RIMMs transfer data in 16-bit chunks. The faster access and transfer speed generates more heat. An aluminum sheath, called a heat spreader, covers the module to protect the chips from overheating.

RIMMThese are also called RD-RAM or DRD-RAM.They have 184 pins.These modules have two locating notches to avoid risk of confusion with the previous modules.Smaller modules known as SO-RIMM (Small Outline RIMM) have been designed for portable computers. SO RIMM modules have only 160 pins.

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CONCLUSIONMemory is the most essential part of a computer.Two types of Memory Primary Memory and Secondary Memory.And the different types of Memory modules areSingle In-line Memory ModuleDual In-line Memory ModuleRambus In-line Memory Module