Variable dynamic memory refresh

1. A method, comprising:

refreshing a first region of a memory at a first refresh rate;

characterizing the first region to measure data retention characteristics of the first region by:

copying data from the first region of the memory to a storage resource,

writing a pattern to the first region of the memory,

waiting for a retention time period, and

reading the first region to obtain read data; and

refreshing a second region of the memory at a second refresh rate that is different than the first refresh rate.

2. The method of claim 1 , wherein the first region includes one or more pages of the memory and the second region includes one or more additional pages of the memory.

3. The method of claim 1 , wherein the first region includes one or more rows of the memory and the second region includes one or more additional rows of the memory.

4. The method of claim 1 , wherein the memory is a dynamic random access memory device.

5. The method of claim 1 , further comprising adjusting the retention time period when the read data does not match the pattern.

6. The method of claim 1 , further comprising storing the retention time period as a first refresh interval when the read data matches the pattern.

7. The method of claim 1 , further comprising adjusting the first refresh rate to compensate for a measured temperature compared with a reference temperature.

8. The method of claim 1 , further comprising adjusting the first refresh rate to compensate for a measured voltage level compared with a reference voltage level.

9. The method of claim 1 , further comprising mapping writes to a third region of the memory and reads from the third region of the memory to the storage resource.

10. The method of claim 1 , further comprising:

characterizing a third region to measure data retention characteristics of the third region;

determining a third refresh rate based on the data retention characteristics of the third region; and

determining that the third refresh rate is greater than the first refresh rate.

11. The method of claim 1 , further comprising storing characterization data for the first region of the memory in a first entry of a table.

12. The method of claim 1 , further comprising combining characterization data for a third region of the memory into the first entry of the table that corresponds to the first region of the memory.

13. The method of claim 1 , wherein the first region of the memory is specified as a single address and each bit of the single address is encoded as a 0, 1, or X value.

14. The method of claim 1 , wherein the first region of the memory is specified using a start address and an end address.

15. The method of claim 1 , wherein a priority is associated with the first region of the memory.

16. The method of claim 1 , further comprising

mapping accesses to the first region of the memory to the storage resource.

17. A system, comprising:

a dynamic memory; and

a memory controller that is coupled to the dynamic memory and configured to:

refresh a first region of the dynamic memory at a first refresh rate;

characterize the first region to measure data retention characteristics of the first region by:

copying data from the first region of the memory to a storage resource,

writing a pattern to the first region of the memory,

waiting for a retention time period, and

reading the first region to obtain read data; and

refresh a second region of the dynamic memory at a second refresh rate that is different than the first refresh rate.

18. The system of claim 17 , wherein the memory controller is further configured to adjust the retention time period when the read data does not match the pattern.

19. The system of claim 17 , wherein the memory controller is further configured to store the retention time period as a first refresh interval when the read data matches the pattern.

20. The method of claim 1 , wherein the storage resource is located within a memory controller that is coupled to the memory.

21. The system of claim 17 , wherein the storage resource is located within the memory controller.

22. The system of claim 17 , wherein the first region includes one or more pages of the memory and the second region includes one or more additional pages of the memory.

23. The system of claim 17 , wherein the first region includes one or more rows of the memory and the second region includes one or more additional rows of the memory.