Method to access memory based on a programmable page limit

• US 6,684,304 B2
• Filed: 01/29/1999
• Issued: 01/27/2004
• Est. Priority Date: 01/29/1999
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Jeddeloh, Joseph M.
• Primary Examiner(s): KIM, HONG CHONG
• Application Number:
  US09/239,911
• Publication Number:
  US 20020078298A1
• Time in Patent Office: 1,824 Days
• Field of Search: 711/170-173, 711/5, 711/202, 711/203, 711/206, 711/208, 711/209, 711/159, 711/133, 711/136, 711/160, 710/10, 713/2
• US Class Current: 711/159
• CPC Class Codes: G06F 12/0215 with look ahead addressing means

Abstract

A method to establish a page limit for use by a memory control device during memory access operations includes establishing a page limit value, receiving a memory access request, and performing a memory access operation in accordance with the established page limit and the memory access request. The established page limit may be a fixed number or it may depend upon the number of banks in the memory and/or the type of service provided by a computer system. The established page limit may also vary during computer system operations in response to memory access characteristics such as page miss and/or hit rates.

Claims

1. A method to access computer memory having a plurality of banks, each bank having a plurality of pages, the method comprising:

establishing a programmable page limit value representing a maximum number of the plurality of pages that may be kept in an open state at one time;

receiving a memory access request; and

performing a memory access operation in accordance with the established page limit value and the memory access request.

2. The method of claim 1, wherein the act of establishing comprises obtaining the page limit value from a user modifiable memory.

3. The method of claim 2, wherein the act of obtaining comprises receiving the page limit value from a basic input-output routine.

4. The method of claim 1, wherein the act of establishing comprises:

determining the number of banks in the computer memory; and

setting the page limit value to a fraction of the determined number of banks.

5. The method of claim 4 wherein the act of setting comprises:

obtaining a fraction value; and

setting the page limit value to a whole number approximately equal to the product of the number of banks in the computer memory and the obtained fraction value.

6. The method of claim 1 wherein the act of setting comprises:

obtaining a first value if a determined type of service is a first type and a second value if the determined type of service is a second type; and

setting the page limit value to the obtained value.

7. The method of claim 1, wherein the act of setting comprises:

determining the number of banks in the computer memory; and

setting the page limit value to a whole number approximately equal to the product of the obtained value and the number of banks in the computer memory.

8. The method of claim 1, wherein the act of performing a memory access operation comprises:

determining if opening a page indicated by the memory request will exceed the established page limit and, if it will, selectively closing a page currently in the open state;

opening the page indicated by the memory request; and

completing the memory access operation.

9. The method of claim 8, wherein the act of selectively closing a page is performed in accordance with a specified replacement policy.

10. The method of claim 9, wherein the specified replacement policy comprises a least recently used replacement policy.

11. The method of claim 10, wherein a specified value of the page miss rate is approximately 50%.

12. The method of claim 11, wherein the act of adjusting the page limit value comprises setting the page limit value to 1.

13. The method of claim 1, wherein the maximum number of the plurality of pages that may be kept in an open state at one time comprises a number less than the total number of pages of the plurality of banks.

17. The method of claim 1, wherein the act of setting comprises:

determining the number of banks in the computer memory; and

setting the page limit value to a whole number approximately equal to the product of the obtained value and the number of banks in the computer memory.

14. A method to access computer memory having a plurality of banks, each bank having a plurality of pages, the method comprising:

establishing a programmable page limit value representing a number of the plurality of pages that may be kept in an open state at one time, the act of establishing comprising determining a type of service provided by a computer system and setting the page limit value based on the determined type of service;

receiving a memory access request; and

performing a memory access operation in accordance with the established page limit value and the memory access request.

15. The method of claim 14, wherein the act of obtaining comprises receiving the page limit value from a basic input-output routine.

16. The method of claim 14, wherein the act of setting comprises:

obtaining a first value if the determined type of service is a first type and a second value if the determined type of service is a second type; and

setting the page limit value to the obtained value.

19. The method of claim 14, wherein the maximum number of the plurality of pages that may be kept in an open state at one time comprises a number less than the total number of pages of the plurality of banks.

18. The method of claim wherein the act of performing a memory access operation comprises:

determining if opening a page indicated by the memory request will exceed the established page limit valve and, if it will, selectively closing a page currently, in the open state;

opening the page indicated by the memory request; and

completing the memory access operation.

20. A method to access computer memory having a plurality of banks, each bank having a plurality of pages, the method comprising:

establishing a programmable page limit value representing a number of the plurality of pages that may be kept in an open state at one time, the act of establishing comprising determining a number of banks in the computer memory and setting the page limit value in response to the determination;

receiving a memory access request; and

performing a memory access operation in accordance with the established page limit value and the memory access request.

21. The method of claim 20, wherein the act of obtaining comprises receiving the page limit value from a basic input-output routine.

22. The method of claim 20, wherein the act of setting comprises:

obtaining a fraction value; and

setting the page limit value to a whole number approximately equal to the product of the number of banks in the computer memory and the obtained fraction value.

23. The method of claim 20, wherein the act of performing a memory access operation comprises:

determining if opening a page indicated by the memory request will exceed the established page limit value and, if it will, selectively closing a page currently in the open state;

opening the page indicated by the memory request; and

completing the memory access operation.

24. The method of claim 20, wherein the maximum number of the plurality of pages that may be kept in an open state at one time comprises a number less than the total number of pages of the plurality of banks.

25. A method to access computer memory having a plurality of banks, each bank having a plurality of pages, the method comprising:

establishing a programmable page limit value representing a number of the plurality of pages that may be kept in an open state at one time;

adjusting the page limit value if a page miss rate is above a specified value;

receiving a memory access request; and

performing a memory access operation in accordance with the established page limit value and the memory access request.

26. The method of claim 25, wherein the specified value of the page miss rate is approximately 50%.

27. The method of claim 25, wherein the act of adjusting the page limit value comprises setting the page limit value to 1.

28. The method of claim 25, wherein the act of performing a memory access operation comprises:

determining if opening a page indicated by the memory request will exceed the established page limit and, if it will, selectively closing a page currently in the open state;

opening the page indicated by the memory request; and

completing the memory access operation.

29. The method of claim 25, wherein the maximum number of the plurality of pages that may be kept in an open state at one time comprises a number less than the total number of pages of the plurality of banks.