Write-precompensation and variable write backoff

1. A method for writing data, comprising:

estimating an amount of additional voltage on an affected cell of a solid-state storage device caused by writing to one or more other cells in the solid-state storage device;

determining a modified write value for the affected cell based at least in part on a desired value for the affected cell and the estimated amount of additional voltage; and

writing the modified write value to the affected cell;

wherein estimating includes:

determining whether the cell is associated with an even page or an odd page;

in the event the cell is associated with an even page, estimating includes using a first estimation process; and

in the event the cell is associated with an odd page, estimating includes using a second estimation process.

2. A method as recited in claim 1 , wherein estimating is based at least in part on a voltage written to the interfering cell.

3. A method as recited in claim 1 , wherein the estimated amount of additional voltage has a first value when the affected cell is associated with an even page and has a second value when the affected cell is associated with an odd page.

4. A method as recited in claim 1 , wherein estimating is based at least in part on a difference between the desired write value and a largest voltage level utilized along a word line.

5. A method as recited in claim 1 , wherein the modified write value is a coarse write value for a coarse write of a multiple pass write.

6. A method as recited in claim 1 , wherein estimating includes: writing a first voltage to an affected cell, reading back a baseline voltage level from the affected cell after writing the first voltage, writing a second voltage to an interfering cell after reading back the first read voltage, and reading back an interfered voltage level from the affected cell after writing the second voltage.

7. A method as recited in claim 6 , wherein estimating further includes computing the difference between the baseline voltage level and the interfered voltage level.

8. A method as recited in claim 1 , wherein estimating includes:

writing a first plurality of voltages to a plurality of affected cells;

reading back a plurality of baseline voltage levels from the plurality of affected cells after writing the first plurality;

writing a second plurality of voltages to an plurality of interfering cells after reading back the first plurality;

reading back a plurality of interfered voltage levels from the affected cell after writing the second plurality; and

averaging the differences.

9. A method as recited in claim 1 , wherein determining includes subtracting the estimated amount of additional voltage from the desired value for the victim affected cell.

10. A method as recited in claim 1 , wherein the solid-state storage device is 2-page interleaved and the method further comprises:

for even-paged affected cells:

estimating an amount of additional voltage from a cell to the left of an affected cell, an amount of additional voltage from a cell to the right of an affected cell, and an amount of additional voltage from a cell above an affected cell; and

summing the amounts of additional voltage from the left, right, and above; and

for odd-paged affected cells: estimating an amount of additional voltage from a cell above an affected cell.

11. A method as recited in claim 1 , wherein estimating includes generating a histogram.

12. A method as recited in claim 11 , wherein estimating further includes obtaining a mean for the histogram and estimating the amount of additional voltage is based at least in part on the mean.

13. A method as recited in claim 12 , wherein estimating further includes obtaining a variance for the histogram and estimating the amount of additional voltage is further based at least in part on the variance.

14. A method as recited in claim 1 , wherein estimating includes generating a linear function with the voltage written to one of said one or more of the other cells as the x-axis and the amount of additional voltage as the y-axis.

15. A method as recited in claim 14 , wherein generating the linear function includes minimizing a mean-squared error.

16. A system for writing data, comprising:

a processor configured to:

estimate an amount of additional voltage on an affected cell of a solid-state storage device caused by writing to one or more other cells in the solid-state storage device;

determine a modified write value for the affected cell based at least in part on a desired value for the affected cell and the estimated amount of additional voltage; and

write the modified write value to the affected cell; and

a memory coupled to the processor and configured to provide the processor with instructions;

wherein the processor is configured to estimate at least in part by:

determining whether the cell is associated with an even page or an odd page;

in the event the cell is associated with an even page, estimating includes using a first estimation process; and

in the event the cell is associated with an odd page, estimating includes using a second estimation process.

17. A computer program product for writing data, the computer program product being embodied in a computer readable medium and comprising computer instructions for:

estimating an amount of additional voltage on an affected cell of a solid-state storage device caused by writing to one or more other cells in the solid-state storage device;

determining a modified write value for the affected cell based at least in part on a desired value for the affected cell and the estimated amount of additional voltage; and

writing the modified write value to the affected cell;

wherein estimating includes:

determining whether the cell is associated with an even page or an odd page;

in the event the cell is associated with an even page, estimating includes using a first estimation process; and

in the event the cell is associated with an odd page, estimating includes using a second estimation process.

18. A method for writing data, comprising:

estimating an amount of additional voltage on an affected cell of a solid-state storage device caused by writing to one or more other cells in the solid-state storage device;

determining a modified write value for the affected cell based at least in part on a desired value for the affected cell and the estimated amount of additional voltage; and

writing the modified write value to the affected cell;

wherein the estimated amount of additional voltage has a first value when the affected cell is associated with an even page and has a second value when the affected cell is associated with an odd page.

19. A method as recited in claim 18 , wherein estimating is based at least in part on a voltage written to the interfering cell.

20. A method as recited in claim 18 , wherein estimating is based at least in part on a difference between the desired write value and a largest voltage level utilized along a word line.

21. A method as recited in claim 18 , wherein the modified write value is a coarse write value for a coarse write of a multiple pass write.

22. A method as recited in claim 18 , wherein estimating includes: writing a first voltage to an affected cell, reading back a baseline voltage level from the affected cell after writing the first voltage, writing a second voltage to an interfering cell after reading back the first read voltage, and reading back an interfered voltage level from the affected cell after writing the second voltage.

23. A method as recited in claim 18 , wherein determining includes subtracting the estimated amount of additional voltage from the desired value for the affected cell.

24. A method as recited in claim 18 , wherein estimating includes generating a histogram.

25. A method as recited in claim 18 , wherein estimating includes generating a linear function with the voltage written to one of said one or more of the other cells as the x-axis and the amount of additional voltage as the y-axis.

26. A method for writing data, comprising:

estimating an amount of additional voltage on an affected cell of a solid-state storage device caused by writing to one or more other cells in the solid-state storage device;

determining a modified write value for the affected cell based at least in part on a desired value for the affected cell and the estimated amount of additional voltage; and

writing the modified write value to the affected cell;

wherein the solid-state storage device is 4-page interleaved and the method further comprises:

for a first set of affected cells:

estimating an amount of additional voltage from a cell to the left of an affected cell, an amount of additional voltage from a cell to the right of an affected cell, and an amount of additional voltage from a cell above an affected cell; and

summing the amounts of additional voltage from the left, right, and above;

for a second and third set of affected cells:

estimating an amount of additional voltage from a cell to the right of an affected cell and an amount of additional voltage from a cell above an affected cell; and

summing the amounts of additional voltage from the right and above;

for a fourth set of affected cells: estimating an amount of additional voltage from a cell above an affected cell.