Abstract:
Systems, methods, and apparatuses, including computer program products, are described for, in at least one implementation, determining a measured slope of a spiral, calibrating radial spacing between servo tracks according to a relationship between a target slope and the measured slope, wherein an amount of calibration for the radial spacing varies directly with the relationship between the target slope and the measured slope, and generating servo tracks according to the calibrated radial spacing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application and claims priority to U.S. application Ser. No. 12/192,981 now U.S. Pat. No. 7,733,335, for “Calibrating Servos,” filed on Aug. 15, 2008, which is incorporated by reference herein in its entirety, which claims priority to U.S. Provisional Application Ser. No. 60/956,001, for “Method to Control Track Pitch in a Self-Servowrite Process,” filed on Aug. 15, 2007, which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The subject matter of this specification relates to servos. 
     BACKGROUND 
     In magnetic-medium-based storage devices, data can be stored on circular, concentric tracks on a magnetic disk surface. A read/write head can retrieve and record data on a magnetic layer of a rotating disk as the head flies on a cushion of air over the disk surface. When retrieving data, magnetic field variations can be converted into an analog electrical signal, which can then be amplified and converted to a digital signal for signal processing. To guarantee the quality of the information stored on and read back from the disk, the read/write head needs to be precisely positioned at substantially the center of a track during both writing and reading. A closed-loop servo system, driven by servo information embedded in a dedicated portion of the track, can be used as a reference for positioning the head. 
     The servo information generally defines the position of the data tracks and is generally written with great accuracy to ensure that the head servo system operates properly. The servo information can be written on each surface as a radially extending set of spokes or wedges. The portion of a servo wedge at a particular track location may contain a sync field, and index mark, a gray coded track number, and two or more fine-positioned offset bursts configured in an echelon across the track. Head positioning relative to a track center can be determined and corrected, if necessary, by reading and noting the respective amplitudes and timings of the offset bursts. 
     A servo writer can be used to write the embedded servo information on the disk surface. A servo writer can include a large base (e.g., granite base) to minimize the effects of vibration. The servo writer also may use precision fixtures to hold the target drive, a precision, laser-interferometer-based actuator arm positioning mechanism to place the arms radially with respect to the axis of rotation of the disks in the drive, and an external clock head to position the servo wedges in time. Conventional servo writers are typically large in size and expensive to be manufactured. Further, as track density increases, the servo writing time required to write the servo information also increases, which can create a bottleneck in the disk drive manufacturing process. 
     Conventional hard disk drives (HDD) increasingly use self-servo-write (SSW) processes to write servo sectors using the same heads that are used to read/write data. In some implementations, servo patterns can be written on a machine readable medium for position control. For example, spirals can be written on a machine readable medium. A servo can use the spirals (e.g., servo on the spirals) to position heads to write servo tracks. Typically, the servo moves in a radial direction across the spirals and measures the time shifts of the spirals. For example, a time shift of a spiral can be defined as an amount of time that corresponds to a difference in circumferential distance from one radial location on a spiral to another radial location on the spiral. The servo can determine radial position measurements from the measured time shifts. The measured time shifts depend on a slope of the spiral. Therefore, the slope of the spiral can affect the placement of individual servo tracks and radial spacing between the servo tracks. Variations or inaccuracies in the slope of the spiral can result in imprecise radial spacing between servo tracks. 
     SUMMARY 
     Methods, systems, and apparatus, including computer program products, are described for calibrating servos, and in some implementations for calibrating spiral servos for use in self-servo-write processes. 
     In one aspect, an apparatus is provided that includes a processing module that determines a measured slope of a spiral, and a calibration module that calibrates radial spacing between servo tracks using the measured slope and a target slope. Other embodiments of this aspect include corresponding systems, methods, and computer program products. 
     One or more implementations can optionally include one or more of the following features. The calibration module can include a scaling submodule that scales target timing information according to a ratio of the target slope to the measured slope to determine the radial spacing. The calibration module can include a scaling submodule that scales a target track pitch according to a ratio of the target slope to the measured slope to determine the radial spacing. The processing module can include a scaling submodule that calibrates the measured slope of the spiral. The processing module can include a detection submodule that determines a gain of a system that includes a voice coil motor and a servo signal. The processing module can include a detection submodule that determines an integrated magnitude of the spiral. The processing module can include a correction submodule that determines noise in the integrated magnitude and removes the noise from the integrated magnitude. The processing module can include a detection submodule that determines a difference between a predicted frequency and an actual frequency of the spiral. 
     In another aspect, a method is provided that includes determining a measured slope of a spiral, and calibrating radial spacing between servo tracks using the measured slope and a target slope. Other embodiments of this aspect include corresponding systems, apparatus, and computer program products. 
     One or more implementations can optionally include one or more of the following features. Calibrating radial spacing can include receiving target timing information; scaling the target timing information according to a ratio of the target slope to the measured slope, producing calibrated timing information; and determining the radial spacing using the calibrated timing information. Calibrating radial spacing can include receiving a target track pitch; scaling the target track pitch according to a ratio of the target slope to the measured slope, producing a calibrated track pitch; and determining the radial spacing using the calibrated track pitch. 
     The spiral can be previously written. Determining a measured slope of a spiral can include determining a first measurement of the measured slope of the spiral; and calibrating the first measurement of the measured slope of the spiral, producing a second measurement of the measured slope of the spiral. 
     Determining a measured slope of a spiral can include determining a gain of a system that includes a voice coil motor and a servo signal. The gain can be a mechanical gain. A magnitude of the gain can be inversely proportional to a magnitude of the measured slope. Determining the gain can include injecting a signal into a controller, determining a control command and a position error, and determining a ratio of the position error to the control command. The method can further include controlling the voice coil motor with the controller. The position error and the control command can be determined in the frequency domain. 
     Determining a measured slope of a spiral can include determining an integrated magnitude of a first signal that includes the spiral. The integrated magnitude can be inversely proportional to the measured slope of the spiral. The method can further include determining noise in the integrated magnitude, and removing the noise from the integrated magnitude. Determining noise can include determining a magnitude of the first signal at an edge of an integration window, and multiplying the magnitude by a number of samples in the integration window. In addition, determining noise can include determining a minimum magnitude of the first signal in an integration window, and multiplying the minimum magnitude by a number of samples in the integration window. Furthermore, determining noise can include determining an integrated magnitude of a second signal that does not include the spiral. 
     Determining a measured slope of a spiral can include determining a predicted frequency for writing the spiral; determining an actual frequency of the spiral; and determining a difference between a target velocity and an actual velocity, where the difference is proportional to a difference between the predicted frequency and the actual frequency. Determining an actual frequency of the spiral can include determining a time between sync patterns of the spiral. 
     Particular embodiments of the subject matter described in this specification can be implemented to realize none, one or more of the following advantages. Calibrating spiral servos for use in self-servo-write processes can (i) increase the accuracy of servo track placement; (ii) increase the accuracy of radial spacing between servo tracks; (iii) increase the yield of useable hard disk drives; and (iv) increase the reliability of hard disk drives by reducing servo issues (e.g., interference between servo tracks) and data track encroachment. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing an example hard disk drive. 
         FIG. 2A  is a diagram showing an example machine readable medium that includes spirals and servo tracks. 
         FIG. 2B  is a diagram showing another example machine readable medium that includes spirals and servo tracks. 
         FIG. 3A  is a diagram showing example spirals and servo tracks of  FIG. 2A . 
         FIG. 3B  is a diagram showing example spirals and servo tracks of  FIG. 2B . 
         FIG. 4A  is a diagram that includes the example spirals of  FIG. 3A . 
         FIG. 4B  is a diagram that includes the example spirals of  FIG. 3B . 
         FIG. 5  includes plots showing example mechanical gains. 
         FIG. 6  is a flow chart showing an example process for determining a slope of a spiral. 
         FIG. 7  includes plots showing example spiral magnitudes and example integrated spiral magnitudes. 
         FIGS. 8A and 8B  are plots showing example read signals and example spiral windows. 
         FIG. 9  is a flow chart showing another example process for determining a slope of a spiral. 
         FIG. 10  is a flow chart showing another example process for determining a slope of a spiral. 
         FIG. 11  is a flow chart showing an example process for calibrating radial spacing between servo tracks. 
         FIGS. 12A-12G  show various example implementations of the described systems and techniques. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a diagram showing an example hard disk drive. The hard disk drive includes a head-disk assembly  100  and drive electronics  150 . The head-disk assembly  100  includes machine readable mediums  110  (e.g., disks), a motor assembly  115 , a head assembly  120 , arms  130 , and heads  132  (e.g., read/write heads). The drive electronics  150  includes a servo control  160  (e.g., a servo controller), signal processing circuitry  170 , and a control  180  (e.g., a controller). The control  180  can direct the servo control  160  to control mechanical operations of the head-disk assembly  100 . For example, the control  180  can direct the servo control  160  to position the heads  132  using the arms  130 . As another example, the control  180  can direct the servo control  160  to control the rotational speed of the machine readable mediums  110 , through the motor assembly  115 . The signal processing circuitry  170  can include a processing module  172  and a calibration module  174 . The processing module  172  can process read signals, write signals, and servo signals, for example. The calibration module  174  can calibrate the signals, timing information, and track pitch, for example. 
       FIG. 2A  is a diagram showing an example machine readable medium  200  that includes spirals  210  and servo tracks  220 . The spirals  210  can be written at a first speed that results in a first slope for the spirals  210 . A servo can move, for example, in a radial direction and use the spirals  210  to control head position, and a head can write the servo tracks  220 . For example, the servo can move the head to a location where the circumferential location of the spiral has shifted a predetermined amount of time (e.g. a spiral shift time) to determine the radial spacing between servo tracks. The radial spacing between the servo tracks can define the track pitch (e.g., radial track density). 
       FIG. 2B  is a diagram showing another example machine readable medium  250  that includes spirals  230  and servo tracks  240 . The spirals  230  can be written at a second speed that results in a second slope for the spirals  230 . The first speed can be greater than the second speed. Therefore, the spirals  210  can be referred to as “faster written” spirals, and the spirals  230  can be referred to as “slower written” spirals. Generally, faster written spirals have slopes that are greater than the slopes of slower written spirals. Because the spirals are used to write servo tracks, the slopes can affect the radial spacing between servo tracks. 
       FIG. 3A  is a diagram showing example spirals and servo tracks of  FIG. 2A .  FIG. 3B  is a diagram showing example spirals and servo tracks of  FIG. 2B . In some implementations, a servo moves in a radial direction until a spiral has shifted a predetermined amount of time t to a location to write a servo track. For example, referring to  FIG. 3A , the servo control  160  can control a head  132  to move from a first servo track  302 , until the circumferential location of spiral  210  has shifted a predetermined amount of time t to a second servo track  304 . Then, the head  132  can write a servo track. Radial spacing  310  can be defined, for example, by the radial distance between adjacent servo tracks (e.g., servo tracks  302  and  304 ). 
     Referring to  FIG. 3B , the spiral  230  is a slower written spiral and has a slope less than the slope of the spiral  210  of  FIG. 3A . Moving until the circumferential location of spiral  230  has shifted for the predetermined amount of time t, the head  132  can travel from a third servo track  312 , to a fourth servo track  314 . The radial spacing  320  between the third servo track  312  and the fourth servo track  314  is less than the radial spacing between the first track  302  and the second servo track  304  of  FIG. 3A . 
     In some implementations, the spirals have previously been written on the machine readable medium. In order to generate substantially a same radial spacing between servo tracks from spirals with different slopes, the predetermined amount of time t can be calibrated. 
       FIG. 4A  is a diagram that includes the example spirals of  FIG. 3A .  FIG. 4B  is a diagram that includes the example spirals of  FIG. 3B . Referring to  FIGS. 4A and 4B , the predetermined amount of time t can be calibrated so that the predetermined amount of time is decreased for spirals that have a slope greater than a target slope. 
     The slope of the spiral determines a relationship between a circumferential location of the spiral and the radial location of the head. The relationship can be expressed as:
 
radial_location∝slope·t.
 
     The radial location of the head can be determined by determining the circumferential location of the spiral, which can be represented by spiral timing. For example, increased circumferential movement of the spiral (e.g., increase in the amount of time shift of the spiral) corresponds to increased radial movement. 
     Because the spiral  210  is a faster written spiral and has a greater slope, the head  132  travels a greater radial distance for the same predetermined amount of time t (e.g., a first spiral shift time) of the faster spiral than a slower written spiral. Therefore, the predetermined amount of time t can be calibrated to equal t 1 , so that the head  132  travels a substantially same radial distance  410  as the radial distance  420  traveled with the predetermined amount of time t 2  (e.g., a second spiral shift time) on the slower written spiral  230 . 
     The slope of a spiral can be determined and used to calibrate the predetermined amount of time. By adjusting the predetermined amount of time, the radial distance between servo tracks can be calibrated. The radial distance between servo tracks, on a single machine readable medium or among different machine readable mediums, for example, can be calibrated so that the radial distances between servo tracks are substantially the same. 
     In some implementations, the slope can be determined by determining a gain of a voice coil motor (e.g., a voice coil motor in the motor assembly  115 ). The processing module  174  can include, for example, a detection submodule that determines the gain of the voice coil motor. For example, the mechanical gain of the voice coil motor can be measured periodically as the heads move across the machine readable medium, as described in further detail below. In some implementations, the slope can be determined by determining a “red-shift” of the pattern within the spiral. The processing module  174  can include, for example, a detection submodule that determines the “red-shift” of the pattern within the spiral. For example, the “red-shift” of the pattern within the spiral can be measured as the head moves across the machine readable medium, as described in further detail below. In some implementations, the slope can be determined by determining an integrated magnitude of the spiral. The processing module  174  can include, for example, a detection submodule that determines the integrated magnitude of the spiral. For example, the integrated magnitude of the spiral can be measured as the head moves across the machine readable medium, as described in further detail below. 
     In some implementations, a plurality of the aforementioned implementations can be used in combination to determine the slope. For example, determining an integrated magnitude of a spiral can provide a relative measurement of the slope of the spiral. The relative measurement can be calibrated using measurements of the slope determined from the gain of the voice coil motor, or from the “red-shift” of the pattern within the spiral. The processing module  174  can include, for example, a scaling submodule that calibrates the relative measurement of the slope. For example, the mechanical gain and the integrated magnitude can be used to determine the slope of one or more spirals at a first radial location. The slope of the one or more spirals at a first radial location, determined by the mechanical gain, can be compared to the slope of the one or more spirals at the first radial location, determined by the integrated magnitude, and used as a reference to calibrate integrated magnitude measurements of slopes of the one or more spirals at other radial locations. As another example, the “red-shift” can be used to determine the slope that is used as a reference to calibrate the integrated magnitude measurements of the slopes of the one or more spirals at the other radial locations. Other implementations are possible. 
       FIG. 5  includes plots  500  and  550  showing example mechanical gains  510 ,  520 ,  530 , and  540 . A mechanical gain can define a reaction of a measured location of a head (e.g., radial position) to a control command from the controller  180 , for example. The control command can be, for example, a current to adjust the velocity of a voice coil motor. Components of a hard disk drive that can affect the mechanical gain can include, but are not limited to, the voice coil motor, arm mechanics (e.g., head assembly  120  and arms  130 ), and the servo signal (e.g., a spiral signal). Characteristics of the servo signal can be determined from a measured mechanical gain. For example, a slope of a spiral can be determined from the measured mechanical gain. In some implementations, the measured mechanical gain can be expressed as the product of a voice coil motor (VCM) gain, electrical gain, and other fixed mechanical gains, divided by the slope of the spiral. Therefore, the slope of the spiral can be expressed as: 
     
       
         
           
             Spiral_slope 
             = 
             
               
                 
                   
                     VCM_gain 
                     · 
                     Electrical_gain 
                     · 
                     Other_fixed 
                   
                   ⁢ 
                   _mechanical 
                   ⁢ 
                   _gains 
                 
                 
                   Measured_mechanical 
                   ⁢ 
                   _gain 
                 
               
               . 
             
           
         
       
     
     The magnitude of a gain (e.g., the measured mechanical gain) is inversely proportional to a magnitude of the slope of the spiral. Referring to plot  500 , the difference between the gains  510  and  520  can show the difference between the slopes of the spirals. For example, at a frequency of 502 Hz, the difference between the gain  510  of a slower written spiral and the gain  520  of a faster written spiral can show the difference between the slopes of the spirals. The track pitch of servo tracks written using the slower written spiral and the faster written spiral will include a difference that is proportional to the difference between the slopes. Spirals with a substantially similar mechanical gain (e.g., as shown in the gains  530  and  540 ), will produce written servo tracks with substantially similar track pitches. 
     In some implementations, the gain can be determined by injecting a signal into a controller (e.g., controller  180 ). For example, a disturbance signal can be injected into position sensing firmware while controlling a head to stay on a predetermined path. A resulting control command and position error can be measured. The mechanical gain can be calculated as the ratio of the measured position error (e.g., timing error) to the control command, in the frequency domain. In some implementations, the measurement and injection can be performed at a single frequency (e.g., at 502 Hz in plot  500 ). 
       FIG. 6  is a flow chart showing an example process  600  for determining a slope of a spiral. The process can include injecting  610  a signal into a controller. For example, the calibration module  172  can inject a signal into the control  180 . A control command and a position error can be determined  620 . For example, the processing module  174  can determine a control command and a position error. A ratio of the position error to the control command can be determined  630 . For example, the calibration module  172  can determine a ratio of the position error to the control command. 
       FIG. 7  includes plots showing example spiral magnitudes  710  and  720 , and example integrated spiral magnitudes  715  and  725 . A reader (e.g., a read head) can read a portion of the spiral  210  to determine a spiral magnitude  710 . The reader can also read a portion of the spiral  230  to determine a spiral magnitude  720 . As shown in  FIG. 7 , the spiral magnitude  710  and the spiral magnitude  720  can be integrated to determine integrated spiral magnitudes  715  and  725 , respectively. The integrated magnitudes are inversely proportional to the slope of a spiral. The integrated magnitudes can depend on, for example, head characteristics (e.g., reader and writer widths) and can be used to determine a relative measurement of the slope of a spiral. 
       FIGS. 8A and 8B  are plots showing example read signals  800  and  810 , and example spiral windows  820  and  830 . In some implementations, noise that is included in the integrated magnitudes can be removed. For example, the processing module  174  can include a correction submodule that determines and removes the noise from the integrated magnitudes. Spiral windows can be used to determine noise in the integrated magnitude. 
     In some implementations, the noise can be determined using an integration window  820  (e.g., a spiral window) centered on a spiral signal  840  (e.g., a spiral in the read signal). The magnitude measurements at the edges  850  of the integration window  820  may not contain a spiral signal. A value of the magnitude, or an average of values of magnitudes, at the edges of the integration window  820  can be determined. The value or the average can be multiplied by a number of samples in the integration window  820  to determine the noise in the integration window  820 . In some implementations, a minimum magnitude measurement in an integration window  820  can be used to determine the noise. The minimum magnitude measurement may not include a spiral signal. The noise can be calculated by multiplying the minimum magnitude measurement by the number of samples in a window. In some implementations, the integration window  830  can be moved to a location on the read signal that does not include a spiral (e.g., the spiral signal  840 ) or a servo track signal (e.g., a signal indicating a servo track). The integrated magnitude of the integration window  830  at that non-spiral location can be used to determine the noise. Other implementations are possible. The noise can be subtracted from the integrated magnitude. 
       FIG. 9  is a flow chart showing another example process  900  for determining a slope of a spiral. The process  900  includes determining  910  an integrated magnitude of a first signal that includes a spiral. For example, the processing module  174  can determine an integrated magnitude of a first signal that includes a spiral. Noise in the integrated magnitude is determined  920 . For example, the processing module  174  can determine noise in the integrated magnitude. Noise from the integrated magnitude is removed  930 . For example, the calibration module  172  can remove noise from the integrated magnitude. 
     In some implementations, the slope can be determined by determining a “red-shift” of the pattern within the spiral. 
       FIG. 10  is a flow chart showing another example process  1000  for determining a slope of a spiral. The process  1000  can determine a slope of a spiral by determining a “red-shift” of the pattern within the spiral. The process  1000  includes determining  1010  a predicted frequency for writing a spiral. For example, the calibration module  172  can determine a predicted frequency for writing a spiral. An actual frequency of the spiral is determined  1020 . For example, the processing module  174  can determine an actual frequency of the spiral, including determining a time between sync patterns of the spiral. A difference between a target velocity and an actual velocity is determined  1030 . For example, a detection submodule of the processing module  174  can determine a difference between a target velocity and an actual velocity. The difference between the predicted frequency and the actual frequency can be proportional to the difference between the target velocity and the actual velocity. 
     The slope and a target slope of a spiral can be used to calibrate radial spacing between servo tracks. In some implementations, the ratio of the target slope to the slope (e.g., a measured slope) can be used to scale target timing information (e.g., the predetermined amount of time). For example, the calibration module  172  can include a scaling submodule that scales the target timing information. The target timing information can be scaled to produce calibrated timing information according to the equation: 
     
       
         
           
             
               calibrated_timing 
               ⁢ 
               _information 
             
             = 
             
               target_timing 
               ⁢ 
               
                 _information 
                 · 
                 
                   
                     target_slope 
                     slope 
                   
                   . 
                 
               
             
           
         
       
     
     The calibrated timing information can be used to determine the radial spacing between servo tracks, as described previously. If the slope is greater than the target slope, then the time can be reduced (e.g., t 1  in  FIG. 4A ). For example, if the spiral  230  of  FIG. 4B  has the target slope, and the slope of the spiral  210  of  FIG. 4A  is greater than the target slope of  FIG. 4B , then the target timing information t 2  can be scaled to produce the calibrated timing information t 1 . If the slope is less than the target slope, then the time can be increased. As another example, if t 1  represents the target timing information and the spiral  210  has the target slope, then t 1  can be scaled to produce the calibrated timing information t 2  for the spiral  230 . 
     In some implementations, a target track pitch can be scaled to determine the radial spacing. For example, the calibration module  172  can include a scaling submodule that scales the target track pitch. The target track pitch can be scaled to produce a calibrated track pitch according to the equation: 
     
       
         
           
             
               calibrated_track 
               ⁢ 
               _pitch 
             
             = 
             
               target_track 
               ⁢ 
               
                 _pitch 
                 · 
                 
                   
                     slope 
                     target_slope 
                   
                   . 
                 
               
             
           
         
       
     
     The calibrated track pitch can be used to determine the radial spacing between servo tracks. If the slope is less than the target slope, then the target track pitch (e.g., radial track density) is decreased to produce the calibrated track pitch. If the slope is greater than the target slope, then the target track pitch is increased to produce the calibrated track pitch. 
       FIG. 11  is a flow chart showing an example process  1100  for calibrating radial spacing between servo tracks. The process  1100  includes determining  1110  a slope of a spiral. For example, the slope of the spiral can be determined using one or more of the implementations described previously. Radial spacing between servo tracks is calibrated  1120  using the slope and a target slope. For example, the calibration module  172  can be used to calibrate the radial spacing between servo tracks using the slope and a target slope. 
       FIGS. 12A-12G  show various example implementations of the described systems and techniques. Referring now to  FIG. 12A , the described systems and techniques can be implemented in a hard disk drive (HDD)  1200 . The described systems and techniques may be implemented in either or both signal processing and/or control circuits, which are generally identified in  FIG. 12A  at  1202 . In some implementations, the signal processing and/or control circuit  1202  and/or other circuits (not shown) in the HDD  1200  may process data, perform coding and/or encryption, perform calculations, and/or format data that is output to and/or received from a magnetic storage medium  1206 . 
     The HDD  1200  may communicate with a host device (not shown) such as a computer, mobile computing devices such as personal digital assistants, cellular phones, media or MP3 players and the like, and/or other devices via one or more wired or wireless communication links  1208 . The HDD  1200  may be connected to memory  1209  such as random access memory (RAM), low latency nonvolatile memory such as flash memory, read only memory (ROM) and/or other suitable electronic data storage. 
     Referring now to  FIG. 12B , the described systems and techniques can be implemented in a digital versatile disc (DVD) drive  1210 . The described systems and techniques may be implemented in either or both signal processing and/or control circuits, which are generally identified in  FIG. 12B  at  1212 , and/or mass data storage of the DVD drive  1210 . The signal processing and/or control circuit  1212  and/or other circuits (not shown) in the DVD drive  1210  may process data, perform coding and/or encryption, perform calculations, and/or format data that is read from and/or data written to an optical storage medium  1216 . In some implementations, the signal processing and/or control circuit  1212  and/or other circuits (not shown) in the DVD drive  1210  can also perform other functions such as encoding and/or decoding and/or any other signal processing functions associated with a DVD drive. 
     The DVD drive  1210  may communicate with an output device (not shown) such as a computer, television or other device via one or more wired or wireless communication links  1217 . The DVD drive  1210  may communicate with mass data storage  1218  that stores data in a nonvolatile manner. The mass data storage  1218  may include a hard disk drive (HDD). The HDD may have the configuration shown in  FIG. 12A . The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The DVD drive  1210  may be connected to memory  1219  such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. 
     Referring now to  FIG. 12C , the described systems and techniques can be implemented in a high definition television (HDTV)  1220 . The described systems and techniques may be implemented in either or both signal processing and/or control circuits, which are generally identified in  FIG. 12C  at  1222 , a WLAN interface and/or mass data storage of the HDTV  1220 . The HDTV  1220  receives HDTV input signals in either a wired or wireless format and generates HDTV output signals for a display  1226 . In some implementations, signal processing circuit and/or control circuit  1222  and/or other circuits (not shown) of the HDTV  1220  may process data, perform coding and/or encryption, perform calculations, format data and/or perform any other type of HDTV processing that may be required. 
     The HDTV  1220  may communicate with mass data storage  1227  that stores data in a nonvolatile manner such as optical and/or magnetic storage devices. At least one HDD may have the configuration shown in  FIG. 12A  and/or at least one DVD drive may have the configuration shown in  FIG. 12B . The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The HDTV  1220  may be connected to memory  1228  such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The HDTV  1220  also may support connections with a WLAN via a WLAN interface  1229 . 
     Referring now to  FIG. 12D , the described systems and techniques may be implemented in a control system of a vehicle  1230 , a WLAN interface and/or mass data storage of the vehicle control system. In some implementations, the described systems and techniques may be implemented in a powertrain control system  1232  that receives inputs from one or more sensors  1236  such as temperature sensors, pressure sensors, rotational sensors, airflow sensors and/or any other suitable sensors and/or that generates one or more output control signals such as engine operating parameters, transmission operating parameters, braking parameters, and/or other control signals to one or more output devices  1238 . 
     The described systems and techniques may also be implemented in other control systems  1240  of the vehicle  1230 . The control system  1240  may likewise receive signals from input sensors  1242  and/or output control signals to one or more output devices  1244 . In some implementations, the control system  1240  may be part of an anti-lock braking system (ABS), a navigation system, a telematics system, a vehicle telematics system, a lane departure system, an adaptive cruise control system, a vehicle entertainment system such as a stereo, DVD, compact disc and the like. Still other implementations are contemplated. 
     The powertrain control system  1232  may communicate with mass data storage  1246  that stores data in a nonvolatile manner. The mass data storage  1246  may include optical and/or magnetic storage devices for example hard disk drives and/or DVD drives. At least one HDD may have the configuration shown in  FIG. 12A  and/or at least one DVD drive may have the configuration shown in  FIG. 12B . The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The powertrain control system  1232  may be connected to memory  1247  such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The powertrain control system  1232  also may support connections with a WLAN via a WLAN interface  1248 . The control system  1240  may also include mass data storage, memory and/or a WLAN interface (all not shown). 
     Referring now to  FIG. 12E , the described systems and techniques can be implemented in a cellular phone  1250  that may include a cellular antenna  1251 . The described systems and techniques may be implemented in either or both signal processing and/or control circuits, which are generally identified in  FIG. 12E  at  1252 , a WLAN interface and/or mass data storage of the cellular phone  1250 . In some implementations, the cellular phone  1250  includes a microphone  1256 , an audio output  1258  such as a speaker and/or audio output jack, a display  1260  and/or an input device  1262  such as a keypad, pointing device, voice actuation and/or other input device. The signal processing and/or control circuits  1252  and/or other circuits (not shown) in the cellular phone  1250  may process data, perform coding and/or encryption, perform calculations, format data and/or perform other cellular phone functions. 
     The cellular phone  1250  may communicate with mass data storage  1264  that stores data in a nonvolatile manner such as optical and/or magnetic storage devices for example hard disk drives and/or DVD drives. At least one HDD may have the configuration shown in  FIG. 12A  and/or at least one DVD drive may have the configuration shown in  FIG. 12B . The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The cellular phone  1250  may be connected to memory  1266  such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The cellular phone  1250  also may support connections with a WLAN via a WLAN interface  1268 . 
     Referring now to  FIG. 12F , the described systems and techniques can be implemented in a set top box  1280 . The described systems and techniques may be implemented in either or both signal processing and/or control circuits, which are generally identified in  FIG. 12F  at  1284 , a WLAN interface and/or mass data storage of the set top box  1280 . The set top box  1280  receives signals from a source  1282  such as a broadband source and outputs standard and/or high definition audio/video signals suitable for a display  1288  such as a television and/or monitor and/or other video and/or audio output devices. The signal processing and/or control circuits  1284  and/or other circuits (not shown) of the set top box  1280  may process data, perform coding and/or encryption, perform calculations, format data and/or perform any other set top box function. 
     The set top box  1280  may communicate with mass data storage  1290  that stores data in a nonvolatile manner. The mass data storage  1290  may include optical and/or magnetic storage devices for example hard disk drives and/or DVD drives. At least one HDD may have the configuration shown in  FIG. 12A  and/or at least one DVD drive may have the configuration shown in  FIG. 12B . The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The set top box  1280  may be connected to memory  1294  such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The set top box  1280  also may support connections with a WLAN via a WLAN interface  1296 . 
     Referring now to  FIG. 12G , the described systems and techniques can be implemented in a media player  1300 . The described systems and techniques may be implemented in either or both signal processing and/or control circuits, which are generally identified in  FIG. 12G  at  1304 , a WLAN interface and/or mass data storage of the media player  1300 . In some implementations, the media player  1300  includes a display  1307  and/or a user input  1308  such as a keypad, touchpad and the like. In some implementations, the media player  1300  may employ a graphical user interface (GUI) that typically employs menus, drop down menus, icons and/or a point-and-click interface via the display  1307  and/or user input  1308 . The media player  1300  further includes an audio output  1309  such as a speaker and/or audio output jack. The signal processing and/or control circuits  1304  and/or other circuits (not shown) of the media player  1300  may process data, perform coding and/or encryption, perform calculations, format data and/or perform any other media player function. 
     The media player  1300  may communicate with mass data storage  1310  that stores data such as compressed audio and/or video content in a nonvolatile manner. In some implementations, the compressed audio files include files that are compliant with MP3 (Moving Picture experts group audio layer  3 ) format or other suitable compressed audio and/or video formats. The mass data storage may include optical and/or magnetic storage devices for example hard disk drives and/or DVD drives. At least one HDD may have the configuration shown in  FIG. 12A  and/or at least one DVD drive may have the configuration shown in  FIG. 12B . The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The media player  1300  may be connected to memory  1314  such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The media player  1300  also may support connections with a WLAN via a WLAN interface  1316 . Still other implementations in addition to those described above are contemplated. 
     A few embodiments have been described in detail above, and various modifications are possible. The disclosed subject matter, including the functional operations described in this specification, can be implemented in electronic circuitry, computer hardware, firmware, software, or in combinations of them, such as the structural means disclosed in this specification and structural equivalents thereof, including potentially a program operable to cause one or more data processing apparatus to perform the operations described (such as a program encoded in a computer-readable medium, which can be a memory device, a storage device, a machine-readable storage substrate, or other physical, machine-readable medium, or a combination of one or more of them). 
     The term “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. 
     A program (also known as a computer program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and it can be deployed in any form, including as a stand alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network. 
     While this specification contains many specifics, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments. 
     Other embodiments fall within the scope of the following claims.