# US 8,543,759 B2 · Method for scheduling memory refresh operations including power states

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- Number: US 8,543,759 B2
- Document ID: US8543759B2
- Status: Granted
- Kind: B2
- Application number: 13/779,343
- Filed: 2013-02-27
- Published: 2013-07-04
- Granted: 2013-09-24
- Earliest claimed: 2011-11-28
- Assignees: International Business Machines Corporation
- Applicants: International Business Machines Corporation
- Inventors: Mark A. Brittain; John S. Dodson; Benjamin L. Goodman; Stephen J. Powell; Jeffrey A. Stuecheli
- Web page: https://patentgrep.com/patent/US8543759B2

## CPC

- G11C 11/40615: {Internal triggering or timing of refresh, e.g. hidden refresh, self refresh, pseudo-SRAMs}
- G06F 13/1694: {Configuration of memory controller to different memory types}
- Y02D 10/00: Energy efficient computing, e.g. low power processors, power management or thermal management
- G11C: STATIC STORES (semiconductor memory devices H10B)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE

## Abstract

A method for performing refresh operations on a rank of memory devices is disclosed. After the completion of a memory operation, a determination is made whether or not a refresh backlog count value is less than a predetermined value and the rank of memory devices is being powered down. If the refresh backlog count value is less than the predetermined value and the rank of memory devices is being powered down, an Idle Count threshold value is set to a maximum value such that a refresh operation will be performed after a maximum delay time. If the refresh backlog count value is not less than the predetermined value or the rank of memory devices is not in a powered down state, the Idle Count threshold value is set based on the slope of an Idle Delay Function such that a refresh operation will be performed accordingly.

## Claims

### Claim 1

A method for performing refresh operations on a rank of memory devices, said method comprising:
in response to a completion of a memory operation, determining whether or not a refresh backlog count is greater than a first predetermined value;
in a determination that said refresh backlog count is greater than said first predetermined value, performing a refresh operation as soon as possible;
in a determination that said refresh backlog count is not greater than said first predetermined value, determining whether or not said refresh backlog count is less than a second predetermined value;
in a determination that said refresh backlog count is not less than said second predetermined value, determining whether or not said refresh backlog count is less than a third predetermined value and said rank of memory devices is in a powered down state;
in a determination that said refresh backlog count is less than said third predetermined value and said rank of memory devices is in a powered down state, setting an Idle Count threshold value to a maximum value such that a refresh operation will be performed after a maximum delay time; and
in a determination that said refresh backlog count is not less than said third predetermined value or said rank of memory devices is not in a powered down state, setting said Idle Count threshold value based on the slope of an Idle Delay Function such that a refresh operation will be performed accordingly.

### Claim 2 (depends on 1)

The method of claim 1, wherein said first predetermined value is 7.

### Claim 3 (depends on 1)

The method of claim 1, wherein said second predetermined value is 3.

### Claim 4 (depends on 1)

The method of claim 1, wherein said third predetermined value is 5.

### Claim 5 (depends on 1)

The method of claim 1, wherein said idle count value is negatively proportional to said refresh backlog count.

### Claim 6 (depends on 1)

The method of claim 1, wherein said method further includes in a determination that said refresh backlog count is less than said second predetermined value, setting said Idle Count threshold value to said maximum value.