Method and apparatus for high accuracy distributed time synchronization using processor tick counters

• US 7,194,556 B2
• Filed: 03/30/2001
• Issued: 03/20/2007
• Est. Priority Date: 03/30/2001
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Rajagopal, Priya, Durham, David M.
• Primary Examiner(s): Follansbee; John
• Assistant Examiner(s): Nguyen; Dustin
• Application Number:
  US09/823,070
• Publication Number:
  US 20020143998A1
• Time in Patent Office: 2,181 Days
• Field of Search: 370/507, 370/335, 713/400, 713/375, 725/111, 375/240, 375/354, 375/373, 709/248
• US Class Current: 709/248
• CPC Class Codes: G06F 1/12 Synchronisation of different clock signals provided by a plurality of clock generators

Abstract

A method and apparatus are provided that allow processing engines to be synchronized to each other with high accuracy. In one embodiment, the invention includes obtaining a processor tick counter value from a first processing engine, comparing the obtained processor tick counter value to a processor tick counter value from a second processing engine and determining a timing offset for synchronizing the first processing engine and the second processing engine using the comparison. The invention may further include obtaining a processor tick counter value by sending a request message from the second processing engine to the first processing engine, and receiving a reply from the first processing engine at the second processing engine. The processor tick counter value at the second processing engine can be determined by recording the time at which the request message is sent and by recording the time at which the reply is received. The invention can further include obtaining a processor frequency from the first processing engine, obtaining a processor frequency from the second processing engine and correcting the timing offset for any difference between the first processing engine frequency and the second processing engine frequency.

Claims

1. A method comprising:

obtaining a processor tick counter value from a first processing engine;

comparing the obtained processor tick counter value to a processor tick counter value from a second processing engine;

determining a timing offset using the comparison; and

sending the timing offset to the first processing engine to apply to the execution of instructions by the first processing engine which are normalized to the timing of the second processing engine.

2. The method of claim 1, wherein obtaining a processor tick counter value comprises sending a request message from the second processing engine to the fast processing engine, and receiving a reply from the first processing engine at the second processing engine.

3. The method of claim 2, wherein the processor tick counter value at the second processing engine is determined by recording a time at which the request message is sent.

4. The method of claim 2, wherein the processor tick counter value at the second processing engine is determined by recording a time at which the reply is received.

5. The method of claim 2 further comprising repeating sending a request message, recording a time, receiving a reply, recording a time and determining a timing offset until the determined timing offsets are within a predetermined variability range.

6. The method of claim 1 further comprising applying a time stamp to a message sent from the second processor, the time stamp being determined by applying the determined timing offset.

7. The method of claim 1 further comprising receiving an instruction having an execution time and interpreting the execution time by applying the determined timing offset.

8. The method of claim 1, further comprising:

obtaining a processor frequency from the first processing engine;

obtaining a processor frequency from the second processing engine; and

correcting the timing offset for any difference between the first processing engine frequency and the second processing engine frequency.

9. A machine-readable medium having stored thereon data representing sequences of instructions which, when executed by a machine, cause the machine to perform operations comprising:

obtaining a processor tick counter value from a first processing engine;

comparing the obtained processor tick counter value to a processor tick counter value from a second processing engine;

determining a timing offset using the comparison; and

sending the timing offset to the first processing engine to apply to the execution of instructions by the first processing engine which are normalized to the timing of the second processing engine.

10. The machine-readable medium of claim 9, wherein the instructions for obtaining a processor tick counter value comprise further instructions which, when executed by the machine, cause the machine to perform further operations comprising sending a request message from the second processing engine to the first processing engine and receiving a reply from the first processing engine at the second processing engine.

11. The machine-readable medium of claim 10, further comprising instructions which, when executed by the machine, cause the machine to perform further operations comprising determining the processor tick counter value at the second processing engine by recording a time at which the request message is sent.

12. The machine-readable medium of claim 10, further comprising instructions which, when executed by the machine, cause the machine to perform further operations comprising determining the processor tick counter value at the second processing engine by recording a time at which the reply is received.

13. The machine-readable medium of claim 9, further comprising instructions which, when executed by the machine, cause the machine to perform further operations comprising:

obtaining a processor frequency from the first processing engine;

obtaining a processor frequency from the second processing engine; and

correcting the timing offset for any difference between the first processing engine frequency and the second processing engine frequency.

14. A synchronized computing network comprising:

a first processing engine having a processor tick counter;

a second processing engine having a processor tick counter;

a communications link to send a value from the processor tick counter of the first processing engine to the second processing engine at one time;

a processor of the second processing engine to compare the processor tick counter value from the first processing engine to a processor tick counter value from the second processing engine, to determine a timing offset using the comparison, and to apply the timing offset to the execution of instructions by the first processing engine which are normalized to the timing of the second processing engine.

15. The synchronized computing network of claim 14, wherein the first processor sends the processor tick counter value as a reply to a request message from the second processing engine.

16. The synchronized computing network of claim 15, wherein the processor tick counter value at the second processing engine is determined by recording a time at which the request message is sent.

17. The synchronized computing network of claim 15, wherein the processor tick counter value at the second processing engine is determined by recording a time at which the reply is received.

18. The synchronized computing network of claim 14, wherein the first processing engine and the second processing engine run at different frequencies and wherein the processor corrects the timing offset for the difference between the first processing engine frequency and the second processing engine frequency.

19. The synchronized computing network of claim 14, wherein the processor of the second processing engine applies a time stamp to a message sent from the second processing engine, the time stamp being determined by applying the determined timing offset.

20. The synchronized computing network of claim 14, wherein the processor of the second processing engine executes an instruction at a time based on the determined timing offset.