memory

Some terms regarding cache memory.

• Cache hit

If data is avialable at first processor send adress of desired data to cache that eventis called cache hit.

• Cache miss

• The performance of cache is measured in cache ratio.It's value is 0.g & aware.Primary memory

• The fast entegrated memory of less capacity is primary memory.Eg:ROM,RAM,Cache e.t.c. These memories have great effect on processing speed of computers. Main memory

Main memory has registers which is called MAR(Memory Adress Register)to be acessed another register is MBR(Memory Buffer Regster)which also has an input & output part through which the data transfer take place to & from the adressed location.

The main function of main memory is READ,WRITE,& CLEAN.

a) READ

READ signal when applied READ contents of a memory locations specified by the MAR in to MBR.

b) WITE

WRITE signal when applied,causes contents of MBR to be witten in the memory location.

c) CLEAR

CLEAR signals have same function as that of READ signal except the data READ is not looded with MBR.

Difference between.

a)Primary memory & secondary memory

• Primary memory

1) It is a semi conductor memory.

2) In memory hierchy.it is placed in highest position due to high speed.

3) It's storing capacity is small.

4) Processor directly acess it.Eg:ROM,RAM.

• primemory

1) It is a magnetic & optical memory.

2) In memory hierchy It is placed in lowest position due to low cast & large in size.

3) It's storing capacity is large.

4) Processor dosen't directly process it.It is acessed through I/O entrance.Eg:floppy disk, hard-disk,CD-ROM,DVD,Pendrive.

b)RAM & ROM

• RAM

1) It stands for Random Acess Memory.

2) It is also called READ/WRITE voalitile memory.

3) It contents is lost if power is off.

4) It is costly.

5) It is divided into static & dynamic ROM.

• ROM

1) It stands for READ omly memory.

2) It is called dead store permanent memory.

3) It retains contents if power is off.

4) It is cheap.

5) It is divided into PROM,EPROM,EEPROM.

c)Static RAM & Dynamic RAM

• Static RAM

1) It holds the information in HIP-HOP circuit consisting 6 transistors is needed in cache cell.

2) It is costly.

• DYNAMIC RAM

1) It requirs less n.o of transistors per memory cell because intermation is stored in stray capictor.Here only 1 transistor is required to form a memory cell.

2) It is cheap.

d) PROM EPROM & EEPROM

• PROM

1) It stands for Programmable Read Only Memory.

2) It is programmable ROM whose controls can be erased.

• EPROM

1) It stands for Erasable Programmable Read Only Memory.

2) Information stored can be erased in ultra voiled expositive.

• EEPROM

1) It stands for Electrically Erasable Read Only Memory.

2) It's contents can be erased by electricty & again it can be programmed like as EPROM.

• Secondary memory

Floppy disk,Hard disk,cd-rom dvd zip disk,pendrive magnetic tape are secondary memory which are used to store data.These memory are also called bank memory because these memories are used to store data for future applications.

• Floppy disk

IBM launched diskette in market to store data & programme in 1972.It is made up of mylar plastic or poly vinyl plastic.It consists of concrete rings(tracks) & redail sector data.Plastic is covered with iron oxide or barium ferrite when magnetic material is magnetized binary 1 is produced & when domagnetized 0 is produced.It's storing capacity is 1.44 mb & rotates with the speed of 360 RPMC(Revolution Per Minute)

• Hard disk

It is the size of dish washer with 50 platters.Each with a two feet diameter.These platters could hold 160 kb of data.Segate technology announced the first win chester 5.25" hard disk drive in 1980.

Some terms used in Hard disk

• Platters

The platters are located on the both sides with a special materials designed to store data on the forms of magnetic platters.The upper most surface of the lower disk are not used as read/write surface.

The platters are mounted in a stock as a spindle driver by a special motor connected to the spindle which rotate at the high speed.Actulators controls the read write head.

In hard disk

- Winchester technique is employed to seal read/write head & disk.

- It's speed is to 5400 to 1500 rpm.

- Measuring unit is big (like GB)

Hard disk has following advantages over floppy disk

- Hard disk can store large amount of data in terms of GB.

- Hard disk store data for large amount of data in terms of GB.

- Hard disk is procted fromdust smoke & External heat but floppy isn't.

- Data are safely stored in hard disk than that of floppy disk.