1. A method of upgrading an entry in a cache comprising a first look-up unit and a second look-up unit, said method comprising: determining whether entries of said first look-up unit are safe, wherein said entries comprise high order bits corresponding to a number of bits of an address less a first clustering level less a first granularity, and wherein said entries comprise low order bits corresponding to said first clustering level; provided entries of said first look-up unit are safe, creating a new entry in said second look-up unit, wherein said new entry comprises entries with high order bits corresponding to the number of bits of said address less a second clustering level less a second granularity, and wherein said new entry comprises entries with low order bits corresponding to said second clustering level; and setting entries of a block within said second look-up unit safe, wherein said block comprises high order bits corresponding to said first granularity and said first clustering level less said second granularity.