Method for increasing a processor operating frequency when other subsystem demands are low

1. A method of operating a disk drive having a processor and a first disk drive subsystem, the method comprising:

determining a host activity measure indicative of a frequency of disk access commands received by the disk drive from a host computer;

comparing the host activity measure against a host activity threshold;

determining a first subsystem activity measure indicative of an activity level of the first subsystem;

comparing the first subsystem activity measure against a first subsystem activity threshold;

determining that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold; and

increasing an operating frequency of the processor based at least in part on the determination that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold, wherein the first subsystem includes a servo subsystem of the disk drive, and wherein the first subsystem activity measure is an average time interval between consecutive operations of arming the servo subsystem for a seek operation.

2. The method of claim 1 , wherein the host activity measure includes an average time interval between completed disk access commands.

3. The method of claim 2 , wherein determining the host activity measure includes:

logging a plurality of time intervals in a circular buffer, each of the plurality of time intervals indicative of time elapsed between consecutive completed disk access commands; and

calculating an average of the plurality of time intervals.

4. The method of claim 3 , wherein the average time interval is calculated upon completion of each disk access command.

5. The method of claim 1 , wherein the first subsystem includes a channel subsystem of the disk drive, and wherein the first subsystem activity measure is an average time interval between consecutive operations of arming the channel subsystem for a read or write operation.

6. The method of claim 1 , wherein the operating frequency of the processor is increased based at least in part on a plurality of consecutive determinations that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold.

7. The method of claim 1 , wherein the operating frequency of the processor is increased by an increase factor based at least in part on a maximum energy allowance of the disk drive.

8. A method of operating a disk drive having a processor and a first disk drive subsystem, the method comprising:

determining a host activity measure indicative of a frequency of disk access commands received by the disk drive from a host computer that includes an average time interval between completed disk access commands based on logging a plurality of time intervals in a circular buffer, each of the plurality of time intervals indicative of time elapsed between consecutive completed disk access commands and calculating an average of the plurality of time intervals wherein the circular buffer has 2 k time intervals logged therein, and calculating the average of the plurality of time intervals includes shifting a sum of the plurality of time intervals by k;

comparing the host activity measure against a host activity threshold;

determining a first subsystem activity measure indicative of an activity level of the first subsystem;

comparing the first subsystem activity measure against a first subsystem activity threshold;

determining that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold; and

increasing an operating frequency of the processor based at least in part on the determination that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold.

9. A method of operating a disk drive having a processor and a first disk drive subsystem, the method comprising:

determining a host activity measure indicative of a frequency of disk access commands received by the disk drive from a host computer that includes an average time interval between completed disk access commands, wherein determining the host activity measure includes passing a time interval indicative of time elapsed between consecutive completed disk access commands through an infinite impulse response low pass filter;

comparing the host activity measure against a host activity threshold;

determining a first subsystem activity measure indicative of an activity level of the first subsystem;

comparing the first subsystem activity measure against a first subsystem activity threshold;

determining that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold; and

increasing an operating frequency of the processor based at least in part on the determination that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold.

10. A method of operating a disk drive having a processor and a first disk drive subsystem, the method comprising:

determining a host activity measure indicative of a frequency of disk access commands received by the disk drive from a host computer;

comparing the host activity measure against a host activity threshold;

determining a first subsystem activity measure indicative of an activity level of the first subsystem;

comparing the first subsystem activity measure against a first subsystem activity threshold;

determining that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold; and

increasing an operating frequency of the processor based at least in part on the determination that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold, wherein the first subsystem includes a channel subsystem of the disk drive, and wherein the first subsystem activity measure is an average time interval between consecutive operations of arming the channel subsystem for a read or write operation and wherein determining the first subsystem activity measure includes

logging a plurality of time intervals in a circular buffer, each of the plurality of time intervals indicative of time elapsed between consecutive operations of arming the channel subsystem and

calculating an average of the plurality of time intervals.

11. The method of claim 10 , wherein the average time interval is calculated upon performing each operation of arming the channel subsystem.

12. The method of claim 10 , wherein the circular buffer has 2 k time intervals logged therein and calculating the average of the plurality of time intervals includes shifting a sum of the plurality of time intervals by k.

13. A method of operating a disk drive having a processor and a first disk drive subsystem, the method comprising:

determining a host activity measure indicative of a frequency of disk access commands received by the disk drive from a host computer;

comparing the host activity measure against a host activity threshold;

determining a first subsystem activity measure indicative of an activity level of the first subsystem;

comparing the first subsystem activity measure against a first subsystem activity threshold;

determining that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold; and

increasing an operating frequency of the processor based at least in part on the determination that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold, wherein the first subsystem includes a channel subsystem of the disk drive, wherein the first subsystem activity measure is an average time interval between consecutive operations of arming the channel subsystem for a read or write operation, and wherein determining the first subsystem activity measure includes passing a time interval indicative of time elapsed between consecutive operations of arming the channel subsystem through an infinite impulse response low pass filter.

14. A method of operating a disk drive having a processor and a first disk drive subsystem, the method comprising:

determining a host activity measure indicative of a frequency of disk access commands received by the disk drive from a host computer;

comparing the host activity measure against a host activity threshold;

determining a first subsystem activity measure indicative of an activity level of the first subsystem;

comparing the first subsystem activity measure against a first subsystem activity threshold;

determining that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold;

increasing an operating frequency of the processor based at least in part on the determination that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold;

determining a second subsystem activity measure indicative of an activity level of a second disk drive subsystem;

comparing the second subsystem activity measure against a second subsystem activity threshold; and

determining that the second subsystem activity measure is indicative of less activity than the second subsystem activity threshold.

15. The method of claim 14 , wherein the first subsystem is a channel subsystem and the second subsystem is a servo system.

16. The method of claim 14 , wherein the first subsystem activity threshold and the second subsystem activity threshold are variable thresholds.

17. A disk drive comprising:

a disk having a disk surface;

a head actuatable over the disk surface and operable to write and read from the disk surface;

a host interface configured to receive disk access commands from a host computer coupled to the disk drive, the disk access commands being associated with a host activity measure indicative of a frequency of the disk access commands;

a first subsystem associated with a first subsystem activity measure indicative of an activity level of the first subsystem, wherein the first subsystem includes a servo subsystem of the disk drive;

a processor configured to operate at an operating frequency; and

a clock coupled to the processor and configured to generate an adjustable timing signal to control the operating frequency, the clock operable to increase the operating frequency based at least in part on the host activity measure being indicative of a greater frequency of disk access commands than a host activity threshold, and the first subsystem activity measure being indicative of less activity than a first subsystem activity threshold, wherein the first subsystem activity measure is an average time interval between consecutive operations of arming the servo subsystem for a seek operation.

18. The disk drive of claim 17 , wherein the host activity measure includes an average time interval between completed disk access commands.

19. The disk drive of claim 18 , further comprising a circular buffer configured to log a plurality of time intervals, each of the plurality of time intervals indicative of time elapsed between consecutive completed disk access commands.

20. The disk drive of claim 17 , wherein the first subsystem includes a channel subsystem of the disk drive, and wherein the first subsystem activity measure is an average time interval between consecutive operations of arming the channel subsystem for a read or write operation.

21. The disk drive of claim 17 , wherein the first subsystem includes a servo subsystem, and wherein the first subsystem activity measure is an average time interval between consecutive operations of arming the servo subsystem for a seek operation.

22. A disk drive comprising:

a disk having a disk surface;

a head actuatable over the disk surface and operable to write and read from the disk surface;

a host interface configured to receive disk access commands from a host computer coupled to the disk drive, the disk access commands being associated with a host activity measure indicative of a frequency of the disk access commands;

a first subsystem associated with a first subsystem activity measure indicative of an activity level of the first subsystem;

a processor configured to operate at an operating frequency;

a clock coupled to the processor and configured to generate an adjustable timing signal to control the operating frequency, the clock operable to increase the operating frequency based at least in part on the host activity measure being indicative of a greater frequency of disk access commands than a host activity threshold, and the first subsystem activity measure being indicative of less activity than a first subsystem activity threshold, wherein the host activity measure includes an average time interval between completed disk access commands; and

an infinite impulse response lowpass filter configured to filter a time interval indicative of time elapsed between consecutive completed disk access commands.

23. A disk drive comprising:

a disk having a disk surface;

a head actuatable over the disk surface and operable to write and read from the disk surface;

a host interface configured to receive disk access commands from a host computer coupled to the disk drive, the disk access commands being associated with a host activity measure indicative of a frequency of the disk access commands;

a first subsystem associated with a first subsystem activity measure indicative of an activity level of the first subsystem, wherein the first subsystem includes a channel subsystem of the disk drive;

a processor configured to operate at an operating frequency;

a clock coupled to the processor and configured to generate an adjustable timing signal to control the operating frequency, the clock operable to increase the operating frequency based at least in part on the host activity measure being indicative of a greater frequency of disk access commands than a host activity threshold, and the first subsystem activity measure being indicative of less activity than a first subsystem activity threshold, wherein the first subsystem activity measure is an average time interval between consecutive operations of arming the channel subsystem for a read or write operation; and

a circular buffer operable to log a plurality of time intervals, each of the plurality of time intervals indicative of time elapsed between the consecutive operations of arming the channel system.

24. A disk drive comprising:

a disk having a disk surface;

a head actuatable over the disk surface and operable to write and read from the disk surface;

a host interface configured to receive disk access commands from a host computer coupled to the disk drive, the disk access commands being associated with a host activity measure indicative of a frequency of the disk access commands;

a first subsystem associated with a first subsystem activity measure indicative of an activity level of the first subsystem, wherein the first subsystem includes a channel subsystem of the disk drive;

a processor configured to operate at an operating frequency;

a clock coupled to the processor and configured to generate an adjustable timing signal to control the operating frequency, the clock operable to increase the operating frequency based at least in part on the host activity measure being indicative of a greater frequency of disk access commands than a host activity threshold, and the first subsystem activity measure being indicative of less activity than a first subsystem activity threshold, wherein the first subsystem activity measure is an average time interval between consecutive operations of arming the channel subsystem for a read or write operation; and

an infinite impulse response lowpass filter operable to filter a time interval indicative of time elapsed between consecutive operations or arming the channel subsystem.

25. A disk drive comprising:

a disk having a disk surface;

a head actuatable over the disk surface and operable to write and read from the disk surface;

a host interface configured to receive disk access commands from a host computer coupled to the disk drive, the disk access commands being associated with a host activity measure indicative of a frequency of the disk access commands;

a first subsystem associated with a first subsystem activity measure indicative of an activity level of the first subsystem;

a processor configured to operate at an operating frequency; and

a clock coupled to the processor and configured to generate an adjustable timing signal to control the operating frequency, the clock operable to increase the operating frequency based at least in part on the host activity measure being indicative of a greater frequency of disk access commands than a host activity threshold, and the first subsystem activity measure being

indicative of less activity than a first subsystem activity threshold; and

a second subsystem associated with a second subsystem activity measure indicative of an activity level of the second subsystem, and wherein the clock is further operable to increase the operating frequency based at least in part on the second subsystem activity measure being indicative of less activity than a second subsystem activity threshold.

26. The disk drive of claim 25 , wherein the first subsystem is a channel subsystem and the second subsystem is a servo system.

27. The disk drive of claim 25 , wherein the first subsystem activity threshold and the second subsystem activity threshold are variable thresholds.

28. A disk drive comprising:

means for determining a host activity measure indicative of a frequency of disk access commands received by the disk drive from a host computer;

means for comparing the host activity measure against a host activity threshold;

means for determining a first subsystem activity measure indicative of an activity level of a first disk drive subsystem, wherein the first subsystem includes a servo subsystem of the disk drive;

means for comparing the first subsystem activity measure against a first subsystem activity threshold;

means for determining that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold; and

means for increasing an operating frequency of a processor based at least in part on the determination that the host activity measure is indicative of a greater frequency of disk access commands than the host activity threshold, and that the first subsystem activity measure is indicative of less activity than the first subsystem activity threshold, wherein the first subsystem activity measure is an average time interval between consecutive operations of arming the servo subsystem for a seek operation.