A cache implements bank-by-bank locking to keep critical code from being flushed out of the cache. A register is maintained to rank the banks from the most recently used to the least recently used. Ordinarily, when code needs to be moved into the cache, the least recently used bank is flushed, the code is moved into that bank, and the register is updated to identify that bank as the most recently used. However, if a bank is designated in a bypass vector as being locked, that bank is bypassed in the maintenance of the register and is thus never identified as the bank to be flushed.