Compare Oracle SPARC and ARM in supporting the page table. The former adopts 2-level caching and a hashed table with the feature of span (the number of pages an entry represent), while the latter uses also 2-level caching and a hybrid 1/2-level hierarchical page table (1-level for big pages and 2-level for small pages). Suppose 100 ns for memory access, 10 ns for 2nd cache access with cache hit ratio of 90%, and 1 ns for 1st cache access with cache hit ratio of 60%, and the remaining 10% for table lookup in the memory. Note that the 1st cache is looked up first before the 2nd cache, and then the table in the memory.