Hardware updated metadata for non-volatile mass storage cache

A method comprising:

• storing usage bits to indicate usage information for entries in a memory, a usage bit to indicate whether a corresponding entry was accessed during a corresponding one of a predetermined number of clock periods;
• updating a usage bit for an entry read from the memory during a writeback cycle to write the read entry back to the memory by checking a current clock period when the memory is accessed, the current clock period being one of a predetermined number of clock periods, and setting a usage bit corresponding to the current clock period;
• resetting usage bits when an address or tag for an entry is changed;
• and
• setting a usage bit corresponding to a current clock period,
• wherein the memory is non-volatile destructive read cache memory.

A machine readable medium having executable instructions comprising:

• a first group of executable instructions to check a current clock period when a memory is accessed, the current clock period being one of a predetermined number of clock periods;
• a second group of executable instructions to set a usage bit corresponding to the current clock period during a writeback cycle to write data read from the memory back to the memory, the usage bit indicating usage information for the data;
• and
• a third group of executable instructions to reset usage bits in response to changing an address or tag for the memory, and to set a usage bit corresponding to a current clock period,
• wherein the memory is non-volatile destructive read cache memory.