Method and system for dynamically adjusting data transfer rates in PCI-express devices

1. A method for configuring an adapter operationally coupled to a host system, comprising:

determining if a number of lanes supported by the adapter is greater than a number X, after a receiver is detected by the adapter; wherein X depends on a throughput capability of the adapter and a data transfer rate; and

setting a first lane operating speed if the number of lanes is less than the number X and setting a second lane operating speed if the number of lanes is greater than the number X.

2. The method of claim 1 wherein the number X is determined by dividing the throughput capability by the data transfer rate.

3. The method of claim 1 , wherein a state machine in a physical layer of a core logic performs lane configuration after receiving information regarding the number of lanes supported by the adapter.

4. The method of claim 3 , wherein the state machine, based on the number of lanes supported by the adapter, sets certain bit values of a first training packet and a second training packet to broadcast link operating speeds.

5. The method of claim 4 , wherein if X is equal to or less than 4, then an operating speed of 5 Ghz is set and during a speed negotiation step, the adapter and another device enter an idle state for a duration during which the first training packet and the second training packet are re-transmitted and both the adapter and the other device initiate a change in operating speed based on information embedded in the re-transmitted first training packet and the second training packet.

6. The method of claim 1 wherein if X is greater than 4, then an operating speed of 2.5 GHz is set.

7. The method of claim 1 , wherein the adapter is a host bus adapter.

8. An adapter operationally coupled to a host system, comprising:

a core logic that receives information from a Physical Coding Sub-layer indicating if a number of lanes supported by the adapter is greater than a number X, after a receiver is detected; wherein X depends on a throughput capability of the adapter and a data transfer rate; and a first lane operating speed is set if the number of lanes is less than the number X and a second lane operating speed is set if the number of lanes is greater than the number X.

9. The adapter of claim 8 , wherein the number X is determined by dividing the throughput capability by the data transfer rate.

10. The adapter of claim 8 , wherein a state machine in a physical layer of the core logic performs lane configuration after receiving information regarding the number of lanes supported by the adapter.

11. The adapter of claim 10 , wherein the state machine, based on the number of lanes supported by the adapter, sets certain bit values of a first training packet and a second training packet to broadcast link operating speeds.

12. The adapter of claim 11 , wherein if X is equal to or less than 4, then an operating speed of 5 Ghz is set and during a speed negotiation step, the adapter and another device enter an idle state for a duration during which the first training packet and the second training packet are re-transmitted and both the adapter and the other device initiate a change in operating speed based on information embedded in the re-transmitted first training packet and the second training packet.

13. The adapter of claim 8 , wherein if X is greater than 4, then an operating speed of 2.5 GHz is set.

14. The adapter of claim 8 , wherein the adapter is a host bus adapter.

15. The adapter of claim 14 , wherein the host bus adapter is operationally coupled to a computing system for transferring data to and from a storage area network.

16. The adapter of claim 8 , wherein the PCI-Express device is operationally coupled to another PCI-Express device for transferring data.