1. A method of storing information in a computer memory, said method comprising the steps of: specifying a set of k data blocks; using block replacement logic to identify whether a selected data block of said set of k data blocks is replaceable; checking a block replacement mask containing k bits corresponding to said k data blocks to identify whether said selected data block is unlocked; and writing new information to said selected data block only if said block replacement mask indicates that said selected data block is unlocked.