Flexible point-to-point memory topology

1. An apparatus comprising:

a plurality of memory devices; and

a control circuit comprising a duplex registered clock driver and a plurality of duplex data buffers, each configured to operate with two channels, said control circuit configured to enable a plurality of access modes for said plurality of memory devices, wherein (i) in a one-channel mode all of said memory devices are accessed using a single selectable channel, (ii) in a two-channel mode a first portion of said plurality of memory devices is accessed using a first channel and a second portion of said plurality of memory devices is accessed using a second channel, and (iii) each of said duplex data buffers comprises one or more control ports, a first input/output port for communicating with a system bus using said first channel, a second input/output port for communicating with said system bus using said second channel, a third input/output port for communicating with said first portion of said plurality of memory devices, and a fourth input/output port for communicating with said second portion of said plurality of memory devices.

2. The apparatus according to claim 1 , wherein said plurality of memory devices and said control circuit are part of a double data rate (DDR) dual in-line memory module (DIMM).

3. The apparatus according to claim 2 , wherein said plurality of memory devices and said control circuit are configured as a fourth generation double data rate (DDR4) dual in-line memory module (DIMM).

4. The apparatus according to claim 1 , wherein:

in said one-channel mode, accesses to all of said memory devices are managed by said duplex registered clock driver and said plurality of duplex data buffers using a single channel selected from said first and second channels; and

in said two-channel mode, access to said first portion of said plurality of memory devices is managed by said duplex registered clock driver and a first portion of said plurality of duplex data buffers using said first channel and accesses to said second portion of said plurality of memory devices is managed by said registered clock driver and a second portion of said plurality of duplex data buffers using said second channel.

5. The apparatus according to claim 1 , wherein said duplex registered clock driver and each of said plurality of duplex data buffers comprise separate circuitry for each channel.

6. The apparatus according to claim 1 , wherein said duplex registered clock driver comprises a control port for said first channel, a control port for said second channel, one or more output ports for said first channel, and one or more output ports for said second channel.

7. The apparatus according to claim 6 , wherein said one or more output ports for said first channel are connected to said first portion of said plurality of memory devices and said one or more output ports for said second channel are connected to said second portion of said plurality of memory devices.

8. The apparatus according to claim 1 , wherein said duplex registered clock driver comprises a data buffer control port connected to each of said plurality of duplex data buffers by a single data buffer control bus.

9. The apparatus according to claim 1 , wherein said duplex registered clock driver comprises a data buffer control port connected to each of said plurality of duplex data buffers by a first data buffer control bus connected to a first control port for commands related to said first channel and a second data buffer control bus connected to a second control port for commands related to said second channel.

10. The apparatus according to claim 1 , wherein said duplex registered clock driver and each of said plurality of duplex data buffers are enabled to service each channel independently.

11. The apparatus according to claim 1 , wherein said duplex registered clock driver and each of said plurality of duplex data buffers are enabled to selectively switch between three operating modes.

12. The apparatus according to claim 11 , wherein:

in a first operating mode said duplex registered clock driver and each of said plurality of duplex data buffers facilitate communication with said plurality of memory devices using said first and second channels;

in a second operating mode, said duplex registered clock driver and each of said plurality of duplex data buffers facilitate communication between all of said plurality of memory devices and said first channel; and

in a third operating mode, said duplex registered clock driver and each of said plurality of duplex data buffers facilitate communication between all of said plurality of memory devices and said second channel.

13. The apparatus according to claim 12 , wherein a portion of said duplex registered clock driver and a portion of each of said plurality of duplex data buffers associated with the channel not used for communication are placed in an idle state in said second and said third operating modes.

14. The apparatus according to claim 1 , wherein each of said duplex data buffers comprises a first channel data path circuit, a second channel data path circuit, and a transaction control logic.

15. The apparatus according to claim 14 , wherein said transaction control logic is configured to control operations of the duplex data buffer based upon commands received via said one or more control ports.

16. The apparatus according to claim 14 , wherein said transaction control logic is enabled to configure said first channel data path circuit and said second channel data circuit for operation in either the two-channel mode or the one-channel mode using either said first channel or said second channel.

17. The apparatus according to claim 1 , wherein:

said first channel data path circuit is coupled between said first input/output port and said third input/output port; and

said second channel data path circuit is coupled between said second input/output port and said fourth input/output port.

18. The apparatus according to claim 1 , wherein said first channel data path and said second channel data path each comprise a write data path and a read data path.

19. The apparatus according to claim 18 , wherein said first channel data path and said second channel data path each comprise a switch coupling said write data paths.

20. The apparatus according to claim 18 , wherein said first channel data path and said second channel data path each comprise a switch coupling said read data paths.