Flash EEprom system

An improved system for writing data files into a Flash EEprom memory comprising:

• a cache memory for temporarily storing data files intended for the Flash EEprom memory, said cache memory able to undergo significantly more write/erase cycles than the Flash EEprom memory;
• means responsive to a system write to the Flash EEprom memory for writing data files into the cache memory instead of the Flash EEprom memory;
• means for identifying each data file in the cache memory;
• means for determining the time since each data file was last written;
• and
• means for first moving data file having the longest time since last written from the cache memory to the Flash EEprom memory when additional space for new data files is required in the cache memory, thereby substantially reducing the number of actual writes and associated stress to the Flash EEprom memory.

An improved system for writing data files into a Flash EEprom memory comprising:

• a cache memory for temporarily storing data files intended for the Flash EEprom memory, said cache memory able to undergo significantly more write/erase cycles than the Flash EEprom memory;
• means responsive to a system write to the Flash EEprom memory for writing data files into the cache memory instead of the Flash EEprom memory;
• a tag memory for storing the identity of data files and the time each data file was last written;
• and
• means for first moving data file having the longest time since last written from the cache memory to the Flash EEprom memory when additional space for new data files is required in the cache memory, thereby substantially reducing the number of actual writes and associated stress to the Flash EEprom memory.

An improved system for writing data files into a Flash EEprom memory comprising:

• a cache memory for temporarily storing data files intended for the Flash EEprom memory, said cache memory able to undergo significantly more write/erase cycles than the Flash EEprom memory;
• means responsive to a system write to the Flash EEprom memory for writing a data file either into the Flash EEprom memory or instead into the cache memory, said responsive means writing to the Flash EEprom when the a previous copy of said data file is not present in the cache memory, and writing to the cache memory when a previous copy of said data file is present in the cache memory;
• and
• means for first moving data files having the longest times since last written from the cache memory to the Flash EEprom memory when additional space for new data files is required in the cache memory, thereby substantially reducing the number of actual writes and associated stress to the Flash EEprom memory.

An improved system for writing data files into a Flash EEprom memory comprising:

• a cache memory for temporarily storing data files intended for the Flash EEprom memory, said cache memory able to undergo significantly more write/erase cycles than the Flash EEprom memory;
• means responsive to a system write to the Flash EEprom memory for writing a data file either into the Flash EEprom memory or instead into the cache memory, said responsive means writing to the Flash EEprom when said data file is last written after the predetermined period of time, and writing to the cache memory when said data file is last written within a predetermined period of time;
• and
• means for first moving data files having the longest times since last written from the cache memory to the Flash EEprom memory when additional space for new data files is required in the cache memory, thereby substantially reducing the number of actual writes and associated stress to the Flash EEprom memory.

An improved system for writing data files into a Flash EEprom memory comprising:

• a cache memory for temporarily storing data files intended for the Flash EEprom memory, said cache memory able to undergo significantly more write/erase cycles than the Flash EEprom memory;
• a tag memory for storing the identity of data files and the time each data file was last written;
• means responsive to a system write to the Flash EEprom memory for writing a data file either into the Flash EEprom memory or instead into the cache memory, said responsive means writing to the Flash EEprom when the data file is not identified in the tag memory, and writing to the cache memory when the data file is identified in the tag memory;
• and
• means for moving first the data files having the longest times since last written from the cache memory to the Flash EEprom memory when additional space for new data files is required in the cache memory, thereby substantially reducing the number of actual writes and associated stress to the Flash EEprom memory.

A memory card adapted to plug into a computer system in a manner to communicate with a system bus and a standard power supply, comprising the following mounted thereon:

• a plurality of EEprom integrated circuit chips, each of said chips including:
• a large number of individually addressable storage cells organized into a plurality of sectors, each sector containing a plurality of said storage cells,
• a plurality of spare storage cells within any of said sectors,
• means responsive to signals on said system bus for erasing all cells in one or more designated sectors without erasing cells in others of said sectors,
• means responsive to signals on said system bus for reading the state of addressed storage cells,
• means responsive to signals on said system bus for programming addressed storage cells to a predetermined state, and
• means responsive to an unsuccessful attempt to either program or erase a storage cell within one of said sectors for substituting one of said spare storage cells therefore while maintaining operation of the remaining cells of said sector.