  1. complete the cache mechanism and add some comment for readable   2. it include three states:     1. shared state: the memory is read and shared with same value in sd card     2. dirty state: the memory is changed and should be writed back     3. miss state: the request memory address is not in the memory
  1. complete the cache mechanism and add some comment for readable
  2. it include three states:
    1. shared state: the memory is read and shared with same value in sd card
    2. dirty state: the memory is changed and should be writed back
    3. miss state: the request memory address is not in the memory

neil-tan/uTensor,neil-tan/uTensor