Different between PROM and EPROM

Different between PROM and EPROM:

                      The difference between PROM and EPROM is as follow; 

PROM

1. PROM is a programmable memory.
2. The user can write instruction on PROM only once. 
3. The instruction written by the user cannot be erased form PROM.
4. If there is an error while writing on PROM it becomes unusable.

It provides less usability as instruction are written only once..

EPROM

1. EPROM is electronically programmable memory.
2. The user can write instructions on EPROM many times.
3. The instructions written by the user can be erased form EPROM. 
4. If there is an error while writing on EPROM it can still be used again. 
5. It provides more usability as instructions are written many times.

Cache Memory

                         A cache (pronounced "cash" ) is a small and very fast memory. it is designed to speed up the transfer of data and instructions. it is located inside or close to the CPU chip. it is faster than RAM. The data and instructions that are most recently or most frequently used by CPU are stored in cache.

The data and instructions are retrieved form RAM when CPU uses them for the first time. A copy of that or instructions is stored in cache. If the required data is found. there is retrieved form cache memory instead of main memory 

Levels of Cache Memory

                         A computer can have several different levels of cache memory. The levels refer to distance form CPU where Levels 1 is the closest. All levels of cache memory are faster than RAM. 

Different levels of cache memory are as follows;

1. Level 1 Cache           
2.  It is also called primary or internal cache. it is built directly into the processor chip. It has small capacity form 8 KB to 128 KB.
3. Level  2 Cache             
4. It is slower than L 1 cache. its storage capacity is more from 64KB to 16 KB. The current processors contains advanced transfer cache on processors chip that is a types of L2  cache. 
5. Level  3 Cache          
6.     This cache is separate form processors chip on the motherboard . It exists on the computer than L2 advanced transfer cache. The personal computer often has up to 8MB of L3 cache.