What is Computer Memory

In  this chapter you will learn about Computer Memory. And you will also find the answers of these questions.

1.What is Memory?

2.Types of Computer Memory.

3.What is RAM ? 

4.What is Flash Memory ?

5.What is ROM

6.What is Cache memory ?

7.Types Of ROM

8.What is DRAM ?

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What is Computer Memory

Introduction:

Memory is one of the functions of the brain that enables to store and remember past events similarly in computer the term memory refers to a chip that stores data. It also enables us to retrieve the stored data. The processor retrieve information stored in the memory for processing data. The storage capacity of a memory depends on the type of the memory packages used

Memory Specifications

memory is selected for the system depending on its motherboard Configuration. The motherboard should support different characteristics

•  Number of Pins
•  Memory Frequency (FSB)    
•  Single Chanel or dual channel Memory 

Number of Pins

Each RAM has certain number of pins or connectors using which RAM communicates with the processor through RAM slots.

Memory Frequency

Front Side Bus (FSB) is used to describe the Data Bus. CPU frequency is set as a multiple of FSB. For example, a CPU of 3.2GHz may have a FSB of 1066MHz. This means that the CPU is set to run 3 times the FSB. The Processor FSB and Memory must work at the same frequency

Single channel and dual channel memory

Generally RAM speed is lower than that of CPU. So CPU has to wait for the RAM memory to deliver data. in a perfect PC. RAM memory Would be as fast as the CPU. RAM increases its data rate by using a technique known as dual Channel.

Single channel memory

Commonly all kinds of memory device are 64 bit device i.e.64 wires connecting the memory controller and memory sockets. These wires are enabled as D0 through D63. The memory data buses are shared among all memory sockets Structure of memory channel is shown in figure 2.1.

(Q. What are the different types of Computer Memory ?)

Types of Memory

Memory can be divided into two types, Volatile memory and Non-volatile memory. Volatile memory

temporarily stores the data. it loses data as soon as the system Power supply is turned off.  Non-volatile memory stores data permanently. It does not lose the data even if the system supply is turned off.

Further, memory is classified into physical, flash and cache memory.

Physical Memory

Physical memory is the total amount of memory installed in the computer. For example if the computer has two 1GB memory modules installed, it has a total of 2GB of physical

Flash

Flash Memory is a type of electric erasable programmable read-only memory (EEPRM). A common use of flash memory is to store BIOS settings in the computer's ROM. Although flash memory was used inside the computer, but attacked many other areas outside the box. Flash memory used for digital cameras, cellular phones, networking hardware and PC cards.

Cache memory

Cache memory is a high speed memory in the CPU that is used for faster access to data. It provides the processor with the most frequently requested data. Cache memory increases performance and allows faster retrieval of data.

(What are the different types of Physical Memory ?)

The different types of Physical Memory are:

RAM - Stands for Random Access Memory, It is a semiconductor-based memory where the CPU or the other hardware devices can road and write data, It temporarily  stores the data and it is a volatile memory, Once the system turns off, it loses the data, As a result, RAM is used as a temporary data storage area.

ROM Stands for Read Only Memory, It stores the data permanently and it is a non-volatile memory, It does not loss the data oven after the system turns off. As a result, ROM is a permanent data storage area.

(What are the The different types of ROM ?)

The different types of ROM are: 

PROM

Stands for the Programmable Read-Only Memory, it stores programs permanently and is a non-volatile memory. Programming the ROM is sometimes referred to as burning and it requires a special machine called a device programmer or ROM burner. Each binary I bit can be thought of as a fuse; when a PROM is programmed, a higher voltage blows or burns the fuses at the desired locations thus turning any given 1 into a 0, Due to this, PROM chips are often referred to as One Time Programmable (OTP) chips.

EPROM — Stands for the Erasable Programmable Read-Only Memory. Ultra-violet (UV) rays can remove the programs from this memory It can be easily recognized by the clear quartz crystal window set on the top of chip. An EPROM eraser is a device that contains a UV light source that erases the chip by causing a chemical reaction, which essentially melts the fuses back together. EEPROM/Flash ROM— Stands for the Electrically Erasable Programmable Read Only Memory. Electrical signal removes the programs from this memory.

EEPROM

can be erased by an electric field, rather than exposed to UV. Also, the data can be erased bit by bit allowing only selected portions of the code to be replaced. But in case of Flash ROM, data is rewritten in blocks of 512 bytes instead of bit by bit, so rewriting is faster. Flash memory can erase or reprogram blocks of bytes where as EEPROM erases individual bytes. This is also called hybrid memory as it reads and writes data similar to the RAM but, maintains data similar to the ROM, it is a mixture of RAM and ROM.

Types of RAM

RAM is the main memory of the computer It holds the data until the system turned on. Once the system is switched off, the data is lost As a result, it is known as the  temporary data storage area.

There are two types of RAM, Static RAM and Dynamic RAM.

Static Random Access Memory (SRAM) 

What is SRAM ? 

SRAM is a type of semiconductor memory. It stores the data as long as the power supplied to the system. Once the power is turned off or is lost temporarily, data stored in SRAM is lost. SRAM uses six transistors for each memory cell. Due to more number of transistors present in the cell, the cells do not refresh frequently. Hence, tine data is stored for longer period. Refreshing a cell means re-writing data in a cell.

SRAM is faster in accessing data. The data accessing speed of SRAM makes it behave like a cache memory. SRAM is expensive as compared to DRAM. Example of SRAM is all types of cache memory

Dynamic Random Access Memory (DRAM)

What is DRAM ?The lifetime of the data in DRAM is very short. It is approximately for four milliseconds. The data in DRAM are stored in memory cells. Each memory cell contains a pair of a transistor and a capacitor. Each memory cell is referred as a bit of data, the smallest amount of information that the system can work with. The memory cells  of DRAM are refreshed by the DRAM controller after every few milliseconds to retain the data in the memory

The cells in DRAM are arranged in rows and columns. Each cell has a row and a column reference number. DRAM accesses the data using the cell reference number less expensive number. DRAM is less expensive than SRAM.

Types of DRAM

Different types of DRAMs which are used in a desktop computer are:

SDRAM            184 Pins

RD RAM           184 Pins

DDRI RAM       184 Pins

DDR2 RAM       240 Pins

DDR3 RAM       240 Pins

DDR4 RAM       240 Pins