Basis for Comparison | Primary Memory | Secondary Memory |
---|---|---|
Basic | Primary memory is directly accessible by Processor/CPU. | Secondary memory is not directly accessible by CPU. |
Altered Name | Main memory. | Auxiliary memory. |
Data | Instructions or data to be currently executed are copied to main memory. | Data to be permanently stored is kept in secondary memory. |
Volatility | Primary memory is usually volatile. | Secondary memory is non-volatile. |
Formation | Primary memories are made of semiconductors. | Secondary memories are made of magnetic and optical material. |
Access Speed | Accessing data from primary memory is faster. | Accessing data from secondary memory is slower. |
Access | Primary memory is accessed by the data bus. | Secondary memory is accessed by input-output channels. |
Size | The computer has a small primary memory. | The computer has a larger secondary memory. |
Expense | Primary memory is costlier than secondary memory. | Secondary memory is cheaper than primary memory |
Memory | Primary memory is an internal memory. | Secondary memory is an external memory. |
RAM | ROM | |
---|---|---|
1. | Stands for Randon-access Memory | Stands for Read-only memory |
2. | RAM is a read and write memory | Normally ROM is read only memory and it can not be overwritten. However, EPROMs can be reprogrammed |
3. | RAM is faster | ROM is relatively slower than RAM |
4. | RAM is a volatile memory. It means that the data in RAM will be lost if power supply is cut-off | ROM is permanent memory. Data in ROM will stay as it is even if we remove the power-supply |
5. | There are mainly two types of RAM; static RAM and Dynamic RAM | There are several types of ROM; Erasable ROM, Programmable ROM, EPROM etc. |
6. | RAM stores all the applications and data when the computer is up and running | ROM usually stores instructions that are required for starting (booting) the computer |
7. | Price of RAM is comparatively high | ROM chips are comparatively cheaper |
8. | RAM chips are bigger in size | ROM chips are smaller in size |
9. | Processor can directly access the content of RAM | Content of ROM are usually first transferred to RAM and then accessed by processor. This is done in order to be able to access ROM content at a faster speed. |
10. | RAM is often installed with large storage. | Storage capacity of ROM installed in a computer is much lesser than RAM |