computer memory

Computer Memory, RAM and ROM


Computer Memory, RAM and ROM

Computer Memory is used to store data and instructions. It is a  storage space in the computer system. CPU fetched information from computer memory (RAM) for processing this process is very fast.

Types of Computer Memory :

1. Primary Memory / Volatile Memory.
2. Secondary Memory / Non Volatile Memory.

1. Primary Memory / Volatile Memory :

It is main memory of computer system. It is called temporary memory  that is if power is off then all the data stored in RAM gets erased for this reason it is also called as  volatile memory.

RAM (Random Access Memory) is an example of Primary Memory. RAM usually hold  data/ instructions. Whenever we work on the computer,in other words we may say that we are working on a RAM there fore it very important to save the data ,once we saved data it gets saved in permanent storage like a hard disk.

Computer Memory, RAM DDR

Types of RAM Modules :
Memory modules are circuit cards made up of memory chips, and a few other components.

Single In-line Memory Modules (SIMM) :
SIMM modules have several memory chips on its circuit board.

There are two types of SIMM modules :

i) 30-pin SIMM modules

ii)72-pin SIMM modules.

Dual In-Line Memory Modules (DIMM) :

DIMM is same as SIMMS the only difference is DIMM (Dual In-Line Memory Modules) has two different signal pins on each side.

DIMM have 168 pins.

Rambus In-Line Memory Module (RIMM) :
Rambus inline memory modules (RIMMs) use Rambus Dyamic RAM (RDRAM) chips.
A RIMM package using RDRAM

DDR SDRAM (Double Data Rate SDRAM) :
The next generation of SDRAM is DDR, which has more  bandwidth than  SDRAM this is because it improve memory clock speed to at least 200 MHz.Mostly RAM only transmits data on the rising edge,but DDR SDRAM transferring data on the rising and falling edges of the clock signal which doubling the performance of a chip, it is also know as double pumping.

Computer Memory, DDR RAM,SDRAM

DDR2 SDRAM(Double Data Rate Two SDRAM) :
DDR2 is double speed faster then  DDR SDRAM. This is because it  improved bus signal. The prefetch buffer of DDR2 is 4 bit(double of DDR SDRAM).

Computer Memory, RAM DDR2

DDR3 SDRAM(Double Data Rate Three SDRAM) :

Compare to DDR2 modules DDR3 consume less power which allowing low operating voltage (1.5 V, compared to DDR2’s 1.8 V or DDR’s 2.5 V).

Computer Memory, RAM DDR3

DDR4 SDRAM (Double Data Rate Fourth SDRAM) :
DDR4 SDRAM provides the lower operating voltage (1.2V) and higher transfer rate. The transfer rate of DDR4 is 2133~3200 MT/s.

Computer Memory, RAM DDR4

It is easy to differentiate each RAM module by its notch or cut position.

Please Note : Each type of RAM has a cut or a notch on different positions you can see on figure below.

Computer Memory, RAM

2. Secondary Memory / Non Volatile Memory.

ROM acronym for read-only memory is an example of secondary or non volatile memory .Once data has been written onto a ROM chip, it cannot be removed and can only be read. ROM does not erase it data even when the computer is turned off. ROM is referred to as being nonvolatile.

Kencorner ROM

Permanent memory(ROM) is of 4 types.

ROM (Read only memory).
It is mostly impossible to changed the contains of ROM one manufactured. It is the static form of permanent memory. You cannot change the contents once the data has been written to it.

PROM (Programmable Read Only Memory).
The hardware chip that can be programmed once is called PROM. Special Programmable kits are used to program the electronic chips.

EPROM (Erasable Programmable Read Only Memory).
This type of ROM has a small window on its top. If this window is exposed to UV light for a specific period of time, all the previous data is deleted. You can re-program it after the data has been completely removed.

EEPROM (Electrically Erasable Read Only Memory).
This is the most used type of permanent memory. You can easily erase the data with a software program. BIOS on the motherboard is an example of EEPROM.

Cache Memory

Cache memory is a very high speed semiconductor memory which can speed up the CPU. It is buffer between the CPU and the main memory.
It is much faster than main memory, basically it stores the program that can be executed within a short period of time.It has limited capacity also it is very expensive.



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