In Computer  hardware RAM stands for Random Access Memory which acts as internal memory of  CPU. It allows CPU store data, program, and program results when you switch on the computer. It is the read and write memory of a computer, which means the information can be written to it as well as read from it. 

RAM is a volatile memory which  means it doesn't store data or instruction for long time. It stores data as long as  power is shut down. When we power the computer , the data from hard Disk and SSD stores in RAM. The Benefit of loading data into RAM is that reading data from RAM is much faster than Hard Drives. 

RAM comes in a form of   chip on motherboard and it is the main memory of computer , it is faster to write and Read as compared to the HDD and SSD. 


Types of RAM

Integrated RAM chips can be of two type:

1) Dynamic RAM


Dynamic RAM (DRAM) is a type of Random access Memory , which is made up of memory cell . It is integrated circuit made of millions of transistor and capacitors which is extremely small in size. The capacitors carry a bit of information in it , either 0 or 1 and transistor acts as a switch .

The capacitor needs to be refreshed after regular intervals to maintain the charge in the capacitor. This is the reason it is called dynamic RAM as it needs to be refreshed continuously to maintain its data or it would forget what it is holding. This is achieved by placing the memory on a refresh circuit that rewrites the data several hundred times per second. The access time in DRAM is around 60 nanoseconds.  


2) Static RAM





Static RAM (SRAM) is a type of Random access memory that stores data as long as it receives power.  It is made up of memory cells and is called a static RAM as it does not need to be refreshed on a regular basis because it does not need the power to prevent leakage, unlike dynamic RAM. So, it is faster than DRAM.

 The Static RAM is fast because of the six transistor configuration of circuit that maintains flow of current in one direction or other direction The 0 or 1 state can be written and read instantly without waiting for the capacitor to fill up or drain. The early asynchronous static RAM chips performed read and write operations sequentially, but the modern synchronous static RAM chips overlap read and write operations.


 Difference between Static RAM (SRAM) & Dynamic RAM                                                      (DRAM)




SRAM

DRAM

It is a static memory as it does not need to be refreshed repeatedly.

It is a dynamic memory as it needs to be refreshed continuously or it will lose the data.

Its memory cell is made of 6 transistors. So its cells occupy more space on a chip and offer less storage capacity (memory) than a DRAM of the same physical size.

Its memory cell is made of one transistor and one capacitor. So, its cells occupy less space on a chip and provide more memory than a SRM of the same physical size.

It is more expensive than DRAM and is located on processors or between a processor and main memory.

It is less expensive than SRAM and is mostly located on the motherboard.

It has a lower access time, e.g. 10 nanoseconds. So, it is faster than DRAM.

It has a higher access time, e.g. more than 50 nanoseconds. So, it is slower than SRAM.

It stores information in a bistable latching circuitry. It requires regular power supply so it consumes more power.

The information or each bit of data is stored in a separate capacitor within an integrated circuit so it consumes less power.

It is faster than DRAM as its memory cells don't need to be refreshed and are always available. So, it is mostly used in registers in the CPU and cache memory of various devices.

It is not as fast as SRAM, as its memory cells are refreshed continuously. But still, it is used in the motherboard because it is cheaper to manufacture and requires less space.

Its cycle time is shorter as it does not need to be paused between accesses and refreshes.

Its cycle time is more than the SRAM's cycle time.

Size ranges from 1 MB to 16MB.

Size ranges from 1 GB to 3 GB in smartphones and 4GB to 16GB in laptops.





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