Method and structure of expanding, upgrading, or fixing multi-chip package

1. A system, comprising:

a multi-chip package (MCP) having a plurality of dies, a bottom package substrate for interfacing with a printed circuit board (PCB), and a top package substrate serving as an interface between the MCP and an add-on package, wherein the plurality of dies are stacked between the bottom and top substrates along an axis perpendicular to the bottom and top package substrates; and

the add-on package attached to the multi-chip package to alter functionality of the multi-chip package, wherein the add-on package is located above the top package substrate on the axis.

2. The system of claim 1 , wherein the multi-chip package contains a die that is reserved for new functionality, and is activated upon attachment of the add-on package.

3. The system of claim 1 , wherein the add-on package comprises at least one DRAM memory device such that the combination of the add-on package and the MCP has a greater memory capacity than the MCP alone.

4. The system of claim 1 , wherein the plurality of dies of the multi-chip package comprises at least one non-volatile memory device.

5. The system of claim 1 , wherein the plurality of dies of the multi-chip package comprises at least one of (i) at least one volatile memory device and at least one non-volatile memory device and (ii) at least one processor and at least one memory device.

6. The system of claim 1 , wherein the add-on package is attached to the top package substrate of the multi-chip package.

7. The system of claim 1 , wherein at least two dies are configured to operate in the absence of the add-on package.

8. A multi-chip package (MCP), comprising:

a bottom package substrate for interfacing with a printed circuit board (PCB);

a top package substrate serving as an interface between the MCP and an add-on package;

a plurality of dies, the dies stacked between the bottom and top substrates along an axis perpendicular to the bottom and top package substrates; and

a sensing circuit for detecting the presence of the add-on package attached to the multi-chip package to alter functionality of the multi-chip package, wherein the add-on package is located above the top package substrate on the axis.

9. The MCP of claim 8 , wherein the plurality of dies comprises at least one die that is reserved for new functionality and is activated upon attachment of the add-on package.

10. The MCP of claim 9 , wherein the die reserved for new functionality comprises a memory interface.

11. The MCP of claim 10 , wherein:

the plurality of dies of the MCP comprise of a plurality of dynamic random access (DRAM) memory devices; and

the memory interface comprises a memory interface for a non-volatile memory device in the add-on package.

12. The MCP of claim 8 , wherein the plurality of dies of the multi-chip package comprises at least one volatile memory device and at least one non-volatile memory device.

13. The MCP of claim 8 , wherein the plurality of dies of the multi-chip package comprises at least one processor and at least one memory device.

14. A method, comprising:

sensing, by a multi-chip package (MCP), the attachment of an add-on package to a top package substrate of the MCP, wherein the add-on package is located above the top package substrate on an axis perpendicular to the top package substrate; and

altering functionality of the MCP in response to sensing the attachment of the add-on package.

15. The method of claim 14 , wherein altering functionality of the MCP comprises disabling one or more dies of the MCP.

16. The method of claim 15 , wherein altering functionality of the MCP further comprises enabling functionality of a device on the add-on package to replace the functionality of the one or more dies of the MCP disabled.

17. The method of claim 15 , wherein disabling the one or more dies comprises placing the one or more dies in a deep power down mode state.

18. The method of claim 14 , further comprising:

communicating to a controller to inform new functionality is available.

19. The method of claim 18 , wherein communicating to the controller is accomplished by asserting a status signal from the add-on package to the controller.

20. A method, comprising:

sensing the attachment of an add-on package to a top package substrate of a multi-chip package (MCP);

communicating to a controller to inform new functionality is available, wherein communicating to the controller is accomplished by changing jumper settings on a PCB; and

altering functionality of the MCP in response to sensing the attachment of the add-on package.