text: what is the main difference between main memory and cache memory?   i am not sure how technical you want the answer to be.    main memory (ram) is 1.  cheaper 2.  slower 3.  "smaller in physical size" (per mb) 4.  usually larger in memory capacity (compared to cache) in a computer  because it is smaller in physical size (per mb), you can have a lot of memory in a small physical area.  it is also one of the reasons why it is cheaper  (because less "material" is needed per mb)  on the other hand  cache is 1.  costlier 2.  faster 3.  "larger in physical size" (per mb) 4.  usually smaller in memory capacity (compared to ram) in a computer  you can use the same principles as above (for ram) to  justify points 1, 2, 3, and 4 for cache.    part of the reason why cache is faster is because it has a smaller memory size.    think about how long it takes to find something  you want 1.  in one room 2.  in the entire house  since the room is smaller than a house, it takes less time for you to find something in it.  cache is smaller in memory capacity (compared to ram) for the same reason: to make it quick and easy to find something in it.  a computer stores the data that is "used most often" in cache, so that it can get that data as quickly as possible.  i hope this answers your question.  mahurshi akilla