Memory types

Information about Memory types

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INTRODUCTION
In computingmemoryrefers to the physical devices used to store
programs (sequences of instructions) or data (e.g. programstate
information) on a temporary or permanent basis for use in a
computer or other digital electronic device
.
TYPES OF MEMORIES
Primary or Main Memory
Main memory is divided into two parts :
mRandom Access memory (RAM), (Read
Write Memory (RWM)).
mRead Only Memory (ROM) .

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Random Access Memory (RAM)
A RAM memory chip is an
integrated circuit (IC) made of
millions of transistors and
capacitors. In the most common
form of computer memory,
dynamic random access
memory (DRAM), a transistor
and a capacitor are combines to
create a memory cell, which
represents a single bit of data.
TYPES OF RAM
STATIC RAM
mSemi conductor memory
mUses flip flop to store each bit of memory so does not need to be
periodically refreshed
mFast and consumes low power
mExpensive and has complex structure(6 transistors) so not used
for high capacity applications
DYNAMIC RAM
mStores each bit of memory in capacitor in an intrgrated circuit
mReal capacitors leak charge so capacitors need to be refreshed
periodically
mSimple structure (1 capacitor and 1 transistor per bit) so it has very
high density
READ ONLY MEMORY (ROM)
mNew contents cannot be added
mUsed to store the instructions of routine type,permanent in
nature and used to control or supervise the hardware
Types Of ROM
Programmable Read Only Memory (PROM)
mProgrammed to record the information using a facility PROM
– programmmer
mOnce the information is recorded it cannot be changed

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Erasable Programmable Read Only Memory (EPROM)
mInformation can be erased and chip can be reprogrammed
to record different information using PROM programmer
mIn formation is erased using UV radiations
mIt is of two types- Ultra Voilet Erasable Programmable Read
Only Memory (UEPROM) and Electrically Alterable
Programmable Read Only Memory (EAPROM)
Electrically Erasable Programmable Read Only Memory
(EEPROM)
mMemory is erased by electrical signals
mProvides easy means to store temporary or permanent
information in the form of ROM memory
Cache Memory
mFaster and expensive than RAM
mIt improves the computer’s performance and is less than 512 KB
mProcessor can use it to store frequently accessed data and programs instructions
mIt is of two types – L1 / primary cache(inside microprocessor) and L2/
secondary cache(in the mother board or near the microprocessor)
Secondary Memory
mIt supplements the main memory. It is permanent memory.
mPrograms, data entered into the system, intermediate results
and final results produced are stored in the secondary
memory

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Classification of Memories
Magnetic Based Storage Devices
mPrepared using formatting
mData is recorded on disk in
concentric circular bands called
tracks.
eMAGNETIC TAPE
eFLOPPY DISK
eHARD DISK
Optical Storage Media
mStores large amount of data in some
formats as much as the entire hard disk
mReads data by focusing a laser- generated
beam of light on light on disc’s surface
eCD- ROM discs
eDVD- ROM discs
Memory Hierarchy
Ranking of computer memory
devices, with devices having the
fastest access time at the top of
hierarchy, and devices with slower
access time but larger capacity and
lower cost at lower levels
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