Refresh command control for host assist of row hammer mitigation
A memory device with internal row hammer mitigation couples to a memory controller. The memory controller or host can assist with row hammer mitigation by sending additional refresh cycles or refresh commands. In response to an extra refresh command the memory device can perform refresh for row hammer mitigation instead of refresh for standard data integrity. The memory controller can keep track of the number of activate commands sent to the memory device, and in response to a threshold number of activate commands, the memory controller sends the additional refresh command. With the extra refresh command the memory device can refresh the potential victim rows of a potential aggressor row, instead of simply refreshing a row that has not been accessed for a period of time.
1. A dynamic random access memory (DRAM) device, comprising:
a memory array having multiple rows of memory including a target row;
a counter to track a number of activate commands received for the target row; and
input/output (I/O) hardware to receive an excess refresh command in response to receipt of a threshold number of activate commands for the target row, the excess refresh command to be in excess of a number of refresh commands necessary to refresh the multiple rows within a refresh window, the excess refresh command to indicate a refresh operation without indication of a row address for the refresh operation, wherein the DRAM device is to perform refresh of a victim row in response to the excess refresh command, the victim row subject to row disturb based on access to the target row, wherein the DRAM device is to determine the row address for the refresh operation.
2. The DRAM device of claim 1 , wherein receipt of the threshold number of activates comprises receipt of the threshold number of activates within a specific time window.
3. The DRAM device of claim 2 , wherein receipt of the threshold number of activates within the specific time window comprises a sliding window, where each activate command increases a count and an amount of time decreases the count.
4. The DRAM device of claim 1 , wherein the excess refresh command comprises a refresh command with a tag to indicate that it is for row hammer refresh.
5. The DRAM device of claim 4 , wherein the tag comprises an unused bit of a refresh command encoding.
6. The DRAM device of claim 1 , wherein the threshold number of activate commands is a number lower than a number of activates expected to trigger the row disturb.
7. The DRAM device of claim 1 , wherein the counter comprises a first counter, and further comprising:
other counters to track activate commands for other rows of the memory array.
8. The DRAM device of claim 1 , further comprising:
a comparator to compare a current activate command count to the threshold.
9. A system, comprising:
a memory controller; and
a dynamic random access memory (DRAM) device coupled to the memory controller, the DRAM device including:
a memory array having multiple rows of memory including a target row;
a counter to track a number of activate commands received for the target row; and
input/output (I/O) hardware to receive an excess refresh command from the memory controller in response to receipt of a threshold number of activate commands for the target row, the excess refresh command to be in excess of a number of refresh commands necessary to refresh the multiple rows within a refresh window, the excess refresh command to indicate a refresh operation without indication of a row address for the refresh operation, wherein the DRAM device is to perform refresh of a victim row in response to the excess refresh command, the victim row subject to row disturb based on access to the target row, wherein the DRAM device is to determine the row address for the refresh operation.
10. The system of claim 9 , wherein receipt of the threshold number of activates comprises receipt of the threshold number of activates within a specific time window.
11. The system of claim 10 , wherein receipt of the threshold number of activates within the specific time window comprises a sliding window, where each activate command increases a count and an amount of time decreases the count.
12. The system of claim 9 , wherein the excess refresh command comprises a refresh command with a tag to indicate that it is for row hammer refresh.
13. The system of claim 12 , wherein the tag comprises an unused bit of a refresh command encoding.
14. The system of claim 9 , wherein the threshold number of activate commands is a number lower than a number of activates expected to trigger the row disturb.
15. The system of claim 9 , wherein the counter comprises a first counter, and further comprising:
other counters to track activate commands for other rows of the memory array.
16. The system of claim 9 , the DRAM device further comprising:
a comparator to compare a current activate command count to the threshold.
17. The system of claim 9 , further comprising one or more of:
a host processor device coupled to the memory controller;
a display communicatively coupled to a host processor;
a network interface communicatively coupled to a host processor; or
a battery to power the system.
18. A method comprising:
tracking a number of activate commands received for a target row of multiple rows of a memory array of a memory device;
receiving an excess refresh command in response to receipt of a threshold number of activate commands for the target row, the excess refresh command to be in excess of a number of refresh commands necessary to refresh the multiple rows within a refresh window, the excess refresh command indicating a refresh operation without indication of a row address for the refresh operation;
performing refresh of a victim row in response to the excess refresh command, the victim row subject to row disturb based on access to the target row, wherein the memory device is to determine the row address for the refresh operation.
19. The method of claim 18 , wherein the excess refresh command comprises a refresh command with a tag indicating that it is for row hammer refresh.
20. The method of claim 18 , wherein tracking the number of active commands comprises tracking activate command for multiple rows of the memory array.