Granularity of cache - how small is the line of the cache.
  Blocks per line of cache. 
    In CPU cache, this is a fixed size, equal to or multiple of data bus width.
      32 byte and 64 byte common(Intel), although 128 byte lines exist.

    # Term block is used in wikipedi because current CPUs may work 
      in 8, 16, 32, or 64 bit units depending on the type of data targeted.
      Also, modern buses widths of 32 or 64-bits are common.

  Line arrangement
    All lines are the same length.

    Lines lengths are a power of 2 - 8, 16, 32, 64, etc.

    All segments are divided into the same number of lines.
      Even if no actual memory exists.
   
    All data cached in any particular line are from a single line in main 
      memory and in the same order.
      *All data in a line is local to itself. Consecutive bytes of memory.

    However, adjacent lines may have data from completely different
      segments of memory. 

    In non-split (unified) caches, 
        different lines can hold either code or user data.

Cache in use