Software controlled content addressable memory in a general purpose execution datapath

• US 6,868,476 B2
• Filed: 08/05/2002
• Issued: 03/15/2005
• Est. Priority Date: 08/27/2001
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Bernstein, Debra, Rosenbluth, Mark B., Wolrich, Gilbert
• Primary Examiner(s): MOAZZAMI, NASSER G
• Application Number:
  US10/212,943
• Publication Number:
  US 20030046488A1
• Time in Patent Office: 953 Days
• Field of Search: 711/3, 711/108, 711/152, 365/185.33, 325/40
• US Class Current: 711/108
• CPC Class Codes: G06F 12/0842 for multiprocessing or multitasking
• CPC Class Codes: G06F 9/30021 Compare instructions, e.g. Greater-Than, Equal-To, MINMAX
• CPC Class Codes: G06F 9/3004 to perform operations on memory
• CPC Class Codes: G06F 9/30043 LOAD or STORE instructions; Clear instruction
• CPC Class Codes: G06F 9/383 Operand prefetching cache prefetching G06F12/0862

Abstract

A lookup mechanism provides an input value to a datapath element disposed in an execution datapath of a processor and causes the datapath element to compare the input value to stored identifier values. The lookup mechanism receives from the datapath element a result based on the comparison.

Claims

1. A method of performing a data lookup comprising:

providing input to a first datapath element of a plurality of datapath elements, the plurality of datapath elements disposed in an execution datapath of a processor, the input including selection information and an input value;

determining, based on the selection information, that the first datapath element is selected to perform at least one operation; and

performing the at least one operation using the first datapath element, wherein performing the at least one operation comprises causing the first datapath element to compare the input value to stored identifier values.

2. The method of claim 1 wherein the first datapath element comprises:

a content addressable memory (CAM).

3. The method of claim 2 wherein the CAM includes a plurality of entries that store the identifier values and corresponding entry numbers.

4. The method of claim 3, wherein the result includes status information indicating if a match is found.

5. The method of claim 4 wherein the status information further includes an entry number.

6. The method of claim 5 wherein the entry number corresponds to the matched identifier value if a match is indicated.

7. The method of claim 6 wherein the CAM maintains a Least Recently Used (LRU) list of identifier values.

8. The method of claim 7 wherein, if the status information indicates that a match has not occurred as a result of the comparison, the entry number corresponds to the identifier value that is a LRU identifier value according to the list of LRU identifier values.

9. The method of claim 5 wherein the status information further comprises status associated with the matched identifier value.

10. The method of claim 9 wherein the identifier values are associated with data stored in a memory and the status comprises a lock status indicating that the data associated with the matched identifier value is in the process of being modified.

11. The method of claim 1 wherein providing input comprises executing an instruction having an operand that carries the input value.

12. The method of claim 1 further comprising providing different selection information to the first datapath element and determining, based on the different selection information, that a different datapath element of the plurality of datapath elements is selected to perform one or more operations.

13. The method of claim 1, further comprising generating a result based on comparing the input value to stored identifier values, and wherein providing an input comprises executing a lookup instruction that specifies a source register to supply the operand carrying the input value and a destination register in which the result is to be stored.

14. The method of claim 13 wherein the source and destination registers are registers in a general purpose register file in communication with the execution datapath.

15. A computer program product residing on a computer-readable medium comprising instructions to cause one or more machines to:

provide an input to a first datapath element of a plurality of datapath elements in an execution datapath, the input indicating that the first datapath element is selected to perform one or more operations, thereby causing the first datapath element to compare an input value to stored identifier values; and

receive from the datapath element a result based on the comparison.

16. The computer program product of claim 15 wherein the first datapath element comprises:

a content addressable memory (CAM).

17. The computer program product of claim 16 wherein the CAM includes a plurality of entries that store the identifier values and corresponding entry numbers.

18. The computer program product of claim 17 wherein the result includes status information indicating if a match is found.

19. An apparatus comprising:

a processor;

a memory storing a computer program product residing on a computer-readable medium comprising instructions to cause one or more machines to;

provide an input to a first datapath element in an execution datapath, the input indicating that the first datapath element is selected to perform one or more operations, thereby causing the first datapath element to compare an input value to stored identifier values; and

receive from the datapath element a result based on the comparison.

20. The apparatus of claim 19 wherein the first datapath element comprises:

a content addressable memory (CAM).

21. The apparatus of claim 20 wherein the CAM includes a plurality of entries that store the identifier values and corresponding entry number.

22. The apparatus of claim 21 wherein the result includes status information indicating if a match is found.