Method and apparatus for approximated least-recently-used algorithm memory replacement

The invention is an improved method and apparatus for implementing the "least-recently-used" (LRU) replacement algorithm in a memory. A counter keeps count of the number of memory accesses. Each block in the memory is associated with a time tag that represents an approximation of the age in the memory. The criteria for updating a time tag is based upon the value of the counter and the time tag. The block with a time tag value representing the highest residence time in memory with respect to the other time tags is always replaced first. The time tag for the most recently accessed block is set to a value representing the least residence time in memory and the other time tags are updated based upon their age in the memory.