Circuit for providing chip-select signals to a plurality of ranks of a DDR memory module

1. A circuit configured to be mounted on a memory module comprising a first number of ranks, each rank of the first number of ranks comprising a plurality of double-data-rate (DDR) memory devices that are configured to be activated concurrently with one another and separately from the DDR memory devices of the other ranks by a first number of chip-select signals for receiving and transmitting data having a bit width of the rank, the first number of ranks comprising a first number of DDR memory devices, the memory module configured to be operationally coupled to a computer system, the circuit configurable to:

receive a set of signals comprising bank address signals, a second number of chip-select signals, and row/column address signals from the computer system, the received set of signals capable of controlling a second number of ranks of DDR memory devices that are configured to be activated concurrently with one another and separately from the DDR memory devices of the other ranks for receiving and transmitting data having a bit width of the rank, the second number of ranks comprising a second number of DDR memory devices, the second number of ranks smaller than the first number of ranks, the second number of chip-select signals smaller than the first number of chip-select signals, and the second number of DDR memory devices smaller than the first number of DDR memory devices;

generate phase-locked clock signals in response to clock signals of the computer system, wherein the circuit is configurable to transmit the generated phase-locked clock signals to the DDR memory devices of the first number of ranks; and

provide the first number of chip-select signals to the first number of ranks in response to the phase-locked clock signals, the received bank address signals, the received second number of chip-select signals, and at least one of the received row/column address signals.

2. The circuit of claim 1 , wherein the circuit is further configurable to buffer a plurality of the received row/column address signals during a row access procedure and to transmit the plurality of the received row/column address signals to the first number of ranks during a subsequent column access procedure.

3. The circuit of claim 2 , wherein the plurality of the received row/column address signals are buffered and transmitted by the circuit at least partially in response to the phase-locked clock signals.

4. The circuit of claim 3 , wherein the circuit is configurable so that a single component of the circuit performs two or more of (i) the generating of the phase-locked clock signals, (ii) the buffering of the plurality of the received row/column address signals, and (iii) the providing of the first number of chip-select signals.

5. The circuit of claim 1 , wherein the circuit is further configurable to receive an input command signal from the computer system and to generate and transmit an output command signal to the first number of ranks.

6. The circuit of claim 5 , wherein the circuit is further configurable to respond to the received bank address signals, the received second number of chip-select signals, and the received row/column address signals by selecting at least one rank of the first number of ranks and transmitting the output command signal the selected at least one rank of the first number of ranks.

7. The circuit of claim 1 , wherein the first number of chip-select signals is four and the second number of chip-select signals is two.

8. The circuit of claim 1 , wherein the first number of ranks comprises a plurality of DDR2 memory devices.

9. The circuit of claim 1 , wherein the first number of ranks comprises a plurality of DDR3 memory devices.

10. The circuit of claim 1 , wherein the DDR memory devices of each rank of the first number of ranks is arranged as a row of DDR memory devices.

11. The circuit of claim 1 , wherein the memory module has attributes and the circuit is further configurable to store data accessible to the computer system, wherein the data characterizes the memory module as having attributes that are different from the attributes of the memory module.

12. The circuit of claim 11 , wherein the attributes are selected from a group consisting of: a number of row addresses, a number of column addresses, a number of DDR memory devices, a data width of the DDR memory devices, a memory density per DDR memory device, a number of ranks, and a memory density per rank.

13. The circuit of claim 1 , wherein the circuit is further configurable to store data accessible to the computer system, wherein the data characterizes the memory module as having the second number of ranks.

14. The circuit of claim 13 , wherein the data further characterizes the memory module as having a memory density per rank that is greater than a memory density per rank of the first number of ranks.

15. The circuit of claim 13 , wherein the data further characterizes the memory module as having the second number of DDR memory devices.

16. The circuit of claim 15 , wherein the data further characterizes the memory module as having a memory density per DDR memory device that is greater than a memory density per DDR memory device of the first number of DDR memory devices.

17. A circuit configured to be mounted on a memory module comprising a first number of ranks, each rank of the first number of ranks comprising a plurality of double-data-rate (DDR) memory devices that are configured to be activated concurrently with one another and separately from the DDR memory devices of the other ranks by a first number of chip-select signals for receiving and transmitting data having a bit width of the rank, the first number of ranks comprising a first number of DDR memory devices, the memory module configured to be operationally coupled to a computer system, the circuit comprising:

means for receiving a set of signals comprising bank address signals, a second number of chip-select signals, and row/column address signals from the computer system, the received set of signals capable of controlling a second number of ranks of DDR memory devices that are configured to be activated concurrently with one another and separately from the DDR memory devices of the other ranks for receiving and transmitting data having a bit width of the rank, the second number of ranks comprising a second number of DDR memory devices, the second number of ranks smaller than the first number of ranks, the second number of chip-select signals smaller than the first number of chip-select signals, and the second number of DDR memory devices smaller than the first number of DDR memory devices;

means for generating phase-locked clock signals in response to clock signals of the computer system, the generated phase-locked clock signals configured to be transmitted to the DDR memory devices of the first number of ranks; and

means for providing the first number of chip-select signals to the first number of ranks, wherein the means for providing the first number of chip-select signals is responsive to the phase-locked clock signals, the received bank address signals, the received second number of chip-select signals, and at least one of the received row/column address signals.

18. The circuit of claim 17 , wherein the circuit further comprises means for buffering a plurality of the received row/column address signals during a row access procedure to be transmitted to the first number of ranks during a subsequent column access procedure.

19. The circuit of claim 18 , wherein the means for buffering the plurality of the received row/column address signals is at least partially responsive to the phase-locked clock signals.

20. The circuit of claim 19 , wherein two or more of the means for generating the phase-locked clock signals, the means for buffering the plurality of the received row/column address signals, and the means for providing the first number of chip-select signals are portions of a single component.

21. The circuit of claim 17 , wherein the circuit further comprises means for generating an output command signal to be transmitted to the first number of ranks, the means for generating the output command signal responsive to an input command signal from the computer system.

22. The circuit of claim 17 , wherein the memory module has attributes and the circuit further comprises means to store data accessible to the computer system, wherein the data characterizes the memory module as having attributes that are different from the attributes of the memory module.

23. The circuit of claim 22 , wherein the attributes are selected from a group consisting of: a number of row addresses, a number of column addresses, a number of DDR memory devices, a data width of the DDR memory devices, a memory density per DDR memory device, a number of ranks, and a memory density per rank.

24. A method of using a memory module comprising a first number of ranks, each rank of the first number of ranks comprising a plurality of double-data-rate (DDR) memory devices that are configured to be activated concurrently with one another and separately from the DDR memory devices of the other ranks by a first number of chip-select signals for receiving and transmitting data having a bit width of the rank, the first number of ranks comprising a first number of DDR memory devices, the memory module configured to be operationally coupled to a computer system, the method comprising:

providing a circuit configured to be mounted on the memory module;

using the circuit to receive a set of signals comprising bank address signals, a second number of chip-select signals, and row/column address signals from the computer system, the received set of signals capable of controlling a second number of ranks of DDR memory devices that are configured to be activated concurrently with one another and separately from the DDR memory devices of the other ranks for receiving and transmitting data having a bit width of the rank, the second number of ranks comprising a second number of DDR memory devices, the second number of ranks smaller than the first number of ranks, the second number of chip-select signals smaller than the first number of chip-select signals, and the second number of DDR memory devices smaller than the first number of DDR memory devices;

using the circuit to generate phase-locked clock signals in response to received clock signals of the computer system, and transmitting the generated phase-locked clock signals to the DDR memory devices of the first number of ranks; and

using the circuit to provide the first number of chip-select signals to the first number of ranks in response to the phase-locked clock signals, the received bank address signals, the received second number of chip-select signals, and at least one of the received row/column address signals.

25. The method of claim 24 , further comprising using the circuit to buffer a plurality of the received row/column address signals during a row access procedure and to transmit the plurality of the received row/column address signals to the first number of ranks during a subsequent column access procedure.

26. The method of claim 25 , wherein using the circuit to buffer and to transmit the plurality of the received row/column address signals is performed at least partially in response to the phase-locked clock signals.

27. The method of claim 26 , wherein a single component of the circuit performs two or more of (i) the generating of the phase-locked clock signals, (ii) the buffering of the plurality of the received row/column address signals, and (iii) the providing of the first number of chip-select signals.

28. The method of claim 24 , further comprising using the circuit to receive an input command signal from the computer system and to generate and transmit an output command signal to the first number of ranks.

29. The method of claim 28 , further comprising using the circuit to respond to the received bank address signals, the received second number of chip-select signals, and the received row/column address signals by selecting at least one rank of the first number of ranks and transmitting the output command signal the selected at least one rank of the first number of ranks.

30. The method of claim 24 , wherein the memory module has attributes and the method further comprises using the circuit to store data accessible to the computer system, wherein the data characterizes the memory module as having attributes that are different from the attributes of the memory module.

31. The method of claim 30 , wherein the attributes are selected from a group consisting of: a number of row addresses, a number of column addresses, a number of DDR memory devices, a data width of the DDR memory devices, a memory density per DDR memory device, a number of ranks, and a memory density per rank.