1. A data processing system comprising: a central processing unit executing program instructions to manipulate data; a first level data cache connected to said central processing unit temporarily storing in a plurality of cache lines data for manipulation by said central processing unit, said first level data cache including a plurality of cacheability bits each determining whether data in a corresponding address range is cacheable; a second level cache connected to said first level cache including second level cache temporarily storing in a plurality of cache lines data for manipulation by said central processing unit, said second level cache including a plurality of memory attribute registers each storing memory access attributes for a corresponding address range including said cacheablility bits.