Abstract: A recording apparatus having a microphone unit; and a drive unit adapted to drive a disk medium on which sound collected by the microphone unit is to be recorded. The recording apparatus is capable of changing a rotational speed of the drive unit in accordance with a level of the sound collected by the microphone unit.

Abstract: A motor controlling device includes an acceleration detector for detecting an acceleration of a motor; a motor driver for supplying a driving current to the motor; a heat quantity calculator for calculating a heat quantity generated in the motor at least based on an output from the acceleration detector; and a motor controller for controlling the motor driver based on the heat quantity.

Abstract: An audio player permits compressed or uncompressed audio CDs to be played. The preferred player includes a spindle motor control that causes the CD to be spun at a constant linear velocity that is commensurate with the encoding rate of the file being played. In this manner, the data can be continuously pulled of the CD at just the right rate so that, after being decoded and decompressed, the data can be played. The player also dynamically adjusts its constant linear velocity to the encoding rate of the file being played to permit files on the same disc having different encoding rates to be played.

Abstract: A method of controlling a recording speed of an optical disc recording system includes detecting error information with respect to a level of a servo control signal of the optical disc recording system, and adjusting the recording speed of the optical disc recording system with reference to the error information.

Abstract: Systems and methods are provided through which the current to a spindle motor of the recording medium of a mass storage device is modulated to avoid anomalies in the operation of mass storage device and reduce power consumption. In the example of a disc drive, the current is modulated to prevent expected or predicted disturbances in the air bearing between a read/write head and the recording medium, and to reduce the power consumption when no disturbances are predicted or expected.

Abstract: An optical disk recording method comprising steps of a) performing recording onto the optical disk with a ZCLV method by using zone parameter storage means for storing at least one zone division time and CLV of each zone in a track formed on the optical disk, as zone parameters, for each of a plurality of recording modes and optical disk type determination means for determining the type of the optical disk before recording; b) performing optimization of the recording velocity by detecting, before recording, servo signal fluctuation by accessing the optical disk, by determining maximum recording velocity defined by the speed of a rotational motor rotating the optical disk, and by calculating a changing point of the recording velocity; and c) limiting the speed of the rotational motor, when the servo signal fluctuation at the surface of the optical disk exceeds a reference level and determining the relation between the zone division time and the CLV of each zone.

Abstract: A method and apparatus for reproducing data from an optical disc in which a disc inducing vibration is detected and the speed of the disc is adjusted to an appropriate speed which does not cause vibration. The method includes obtaining the frequency of vibration by subtracting the count value of track traverse pulses at the lowest speed factor from the count value of track traverse pulses at the highest speed factor; and varying the speed factor of reproducing data from the disc based upon a comparison of the obtained frequency of vibration with a predetermined base value.

Abstract: OPC data record in an optical disk is performed at a plurality of record velocities to obtain a maximum record velocity Vlmax. A rotation number of the optical disk is calculated and set, the rotation number being determined in such a manner that the maximum record velocity Vlmax becomes equal to a linear velocity of the optical disk at a detected record position of the optical disk along the radial direction. The optical disk is rotated under a rotation control that a detected actual revolution number of the optical disk becomes equal to the calculated and set rotation number. It is monitored to check whether the record operation of the optical disk at the maximum record velocity Vlmax is normal. If it is detected that the record operation may become abnormal, the maximum record velocity is lowered by ?v1.

Abstract: A device for detecting a crack in an optical disc including a transmitter to propagate an optical signal through the optical disc and a receiver to detect the propagated signal. From the pattern generated from the received signal, a microcontroller makes an analysis to determine if a crack is present on the optical disc. The method may be incorporated into a conventional disc drive as a new crack detection mechanism.

Abstract: A motor controlling device includes an acceleration detector for detecting an acceleration of a motor; a motor driver for supplying a driving current to the motor; a heat quantity calculator for calculating a heat quantity generated in the motor at least based on an output from the acceleration detector; and a motor controller for controlling the motor driver based on the heat quantity.

Abstract: A method, apparatus, and medium for processing data in a Read Only Memory (ROM) drive. The data processing method includes: a ROM drive detecting, buffering, and decoding data at a target location on an optical recording medium; if one of data detection, data buffering, and data decoding fails, checking a CLV speed of the optical recording medium, adjusting a CAV speed of the optical recoding medium, and retrying data detection, data buffering, and data decoding; and if data detection, data buffering, and data decoding are performed successfully, transmitting the decoded data to the host computer. Therefore, it is possible to improve the quality of a ROM drive, by preventing the deterioration of data readability and error generation caused by speed deterioration of the ROM drive, from defects of an optical recording medium.

Abstract: This invention provides method and apparatus for controlling reproduction speed of an optical disk, which detects the magnitude of a disk vibration after initial operation of an optical disk and adjusts the disk rotation speed based upon the vibration magnitude. The method according to this invention comprises the steps of rotating an installed optical disk; detecting the quantity of signal derived from tracking error signals which are combined from signals reproduced from the optical disk when the rotation speed reaches to a predetermined speed; and deciding whether to increase the rotation speed above the predetermined speed based upon the detected quantity of the signal. This invention is able to reproduce an optical disk at the possible maximum speed within allowable speed limit through detecting accurate disk vibration magnitude at the initial operation stage and adjusting the reproduction speed to higher speed.

Abstract: An optical disc playback apparatus which makes an optical disc rotate at given rotational speed and reproduces a record signal based on light reflected from the optical disc. The optical disc playback apparatus comprises a jitter amount detector that detects a jitter amount based on a signal obtained from the reflected light, and a rotational speed adjustment circuit that adjusts the rotational speed of the optical disc based on the jitter amount.

Abstract: An optical head includes an integrated unit (9) having a light-receiving portion for converting reflected light from a disc-shape recording medium (13) into an electric signal and a light source, an objective lens (11), a tracking coil (18a) for driving the objective lens (11) in a radial direction of the disc-shape recording medium (13), a focusing coil (18b) for driving the objective lens (11) in a focus direction of the disc-shape recording medium (13), a signal generation portion (102) for generating a focus error signal and a tracking error signal from the electric signal converted at the light-receiving portion, and a control portion (101) for controlling the tracking coil (18a) and the focusing coil (18b) on the basis of the focus error signal and the tracking error signal.

Abstract: A method, apparatus, and medium for processing data in a Read Only Memory (ROM) drive. The data processing method includes: a ROM drive detecting, buffering, and decoding data at a target location on an optical recording medium; if one of data detection, data buffering, and data decoding fails, checking a CLV speed of the optical recording medium, adjusting a CAV speed of the optical recoding medium, and retrying data detection, data buffering, and data decoding; and if data detection, data buffering, and data decoding are performed successfully, transmitting the decoded data to the host computer. Therefore, it is possible to improve the quality of a ROM drive, by preventing the deterioration of data readability and error generation caused by speed deterioration of the ROM drive, from defects of an optical recording medium.

Abstract: A noise removal circuit of the present invention comprises a 180-degree odd multiple shifting section for outputting a 180-degree shifted signal that is phase-shifted from an input signal by an odd multiple of 180 degrees and difference output section for outputting a difference between the input signal and the 180-degree shifted signal. The noise removal circuit comprises a 360-degree shifting section for outputting a 360-degree shifted signal that is phase-shifted from an input signal by an integral multiple of 360 degrees and sum output section for outputting a sum of the input signal and the 360-degree shifted signal.

Abstract: An exposure apparatus for an optical disc used for eliminating the vibrations in the propagating direction when a rotation mechanism rotates. The slider controller 40 and the spindle controller 41 of the exposure apparatus 1 are activated, and the then the optical disc begins to be rotated by an AC synchronized motor. Through a condensing device 9, laser beams emitted form the laser source 6 are irradiated on the optical disc for exposure. At this time, the optical disc is eccentrically chucked on the rotation mechanism, resulting a rotational vibration of the whole rotation mechanism. A measurer 17 is used for detecting a propagating component of the rotational vibration, and a vibrator controller 42 controls the vibrator 20 as the output of the measurer 17 approaches zero. Therefore, the vibration in the propagating direction of the base 2 is cancelled, and the propagation accuracy is increased and the exposure quality is enhanced.

Abstract: A servo control apparatus of an optical pickup includes an extractor for extracting an error signal from the read signal; a driver for changing the servo position; an equalizer for equalizing the error signal to generate a drive signal; a calculator for calculating an integral value of the error signal for each predetermined angular section of rotation; a memory for storing each of the integral values for one rotation of the recording medium; a detector to detect an occurrence of a dropout; a calculator for calculating a variation by comparing the integral value for an angular section of rotation where the dropout occurred with a stored integral value for the identical angular section of rotation prior to the occurrence of the dropout; and a controller for changing an equalization characteristics of the equalizer in accordance with the variation.

Abstract: When performing writing and/or reading of information to/from an optical disk provided with a wobble including time axis information, an occurrence of a reading error of the time axis information from the wobble is suppressed so that disabled reading of information from the optical disk and an occurrence of a writing error can be prevented. Evaluated parameters such as a CRC error rate of an ATIP signal, an FMDT jitter amount and a phase error between an ATIP synchronization signal and a frame synchronization signal of writing data are evaluated based on a range of set values. When the evaluated parameter is deviated from the range of set values, writing and reading speeds are changed, thereby increasing the reading accuracy of the wobble signal.

Abstract: The present invention relates to a recording speed determining method of a disk device. The present method, when data record is requested from a host through an interface, a disk device can receive size information about data to be recorded and/or the present time from the host, and determine a recording speed of a disk to be suitable for the received size information and/or for a time zone where the device is located. The disk device can determine such data size and time zone information internally. Thus, it is possible to reduce a noise that is caused from disk rotation if the size of data to be recorded is small or when a noise is felt relatively big. Further, it is possible to determine a data recording speed in accordance with a data size.

Abstract: A method for optical axis adjustment of an optical driver is provided for decreasing interference, providing a reliable sensitive determination with respect to the variation of incident angle for facilitating inspection, and precisely adjusting the incident angle to an optimum. An apparatus for optical axis adjustment of an optical driver including a spindle module for rotating disc, a plurality of adjustment devices for adjusting the oblique angle of spindle module, a read/write device for emitting an incident light signal to disc, receiving a reflected light signal from disc, and outputting a reflected voltage signal, a control circuit device for outputting a rotation control signal to the spindle module for rotating the spindle module, outputting a read/write control signal to the read/write device for emitting/receiving incident light signal, and receiving and outputting the reflected voltage signal, and a feedback device for rotating the adjustment devices in response to reflected voltage signal.

Abstract: When a run-away phenomenon of an optical disk occurs, a control circuit detects a rotational direction of the optical disk that runs away by comparing an initial track count value and a braking time track count value. The initial track count value is a value calculated by counting track pulses corresponding to a tracking error signal for a predetermined time when a tracking servo is turned off. The braking time track count value is a value calculated by counting the track pulses corresponding to the tracking error signal for a predetermined time, when a brake pulse is applied to the spindle motor.

Abstract: The invention provides a reliable write method of data on an optical record carrier without changing the conventional configuration of an information recording apparatus. The invention uses the errors occurred in reading ATIP codes and/or the reflected signal from the surface of the record carrier to decide if the storage unit on the record carrier is eligible to store data. The defective storage units are labeled as unrecordable.

Abstract: Apparatus and method for reducing noise and vibrations in a personal computer having at least one disk data-storage device (disk drive), e.g., CDROM drive. The disk drive operation (data reading from or writing to the disk) is afforded by rotation of the disk at a steady rate that is prescribed by a command drawn from related processing block of the computer. The apparatus integrates a disk drive, control program, and data file. For a disk drive under control, the data file lists for each logical operation mode an optimum rotational rate for the drive motor, the optimal value being the lowest value of rotation rate for the drive to provide a sufficient rate of data exchange between the drive and corresponding data processor. In accordance with the optimal disk drive rotation rate value, the program generates necessary control commands to set the disk drive motor to the required rotation rate.

Abstract: An apparatus for changing a recording speed of an optical recording medium by analyzing wobble signals in real time during a recording operation, includes a signal process unit which outputs a cyclic redundancy check (CRC) signal that checks for a generation of errors on the optical recording medium from absolute time in pregroove (ATIP) information output from the optical recording medium during the recording operation, and a speed control unit which changes the recording speed during the recording operation according to a comparison of the CRC signal output from the signal process unit with a reference value. In the apparatus, the recording speed is limited or lowered in response to a signal quality of a recording section being less than an acceptable level during the recording operation. Accordingly, buffer under run and defects of read-in start position and seek fail, which are generated during a ZCLV operation, are prevented.

Abstract: When a deviated gravity disc is reproduced at a higher rate with the disc reproducing apparatus, an excessive vibration is generated and this vibration gives adverse effect on the disc reproducing apparatus and peripheral components/apparatuses, and/or may represent an annoyance to a user. A vibration information detector for detecting vibration of the disc reproducing apparatus or a deviated gravity information detector for detecting amount of gravity deviation of disc is provided, and as a result of such detection of an imbalance (i.e., excessive vibration or mass eccentricity), and a reproducing rate switching control controls sets and limits the reproducing rate of the disc reproducing apparatus to a substitute speed which is lower or higher than a normal reproducing speed.

Abstract: A method for adjusting the writing speed of a data recording device. First, recording media is written to at a writing speed, the Absolute Time In Pregroove Error Rate (ATER) is calculated according to the error codes occurring in Absolute Time In Pregroove (ATIP) on the recording media when writing to the recording media. Then, the writing speed is adjusted according to the Absolute Time In Pregroove Error Rate (ATER) until writing to the recording media is finished.

Abstract: The present invention relates to method and apparatus for controlling disk reproduction speed to extend an operable time of a portable device such as a notebook computer using a battery as a power source. A method for adjusting a disk reproduction speed based on a remaining battery energy according to the present invention, at the part of a portable device such as a notebook computer, detects an amount of the remaining battery energy, and sends a data indicating the detected amount of the remaining battery energy to a connected disk device, and, at the other part of a disk device, reduces a disk reproduction speed based on the data sent by the portable device. The method and apparatus for controlling disk reproduction speed according to the present invention can extend an operable time of the portable device whose operating power is supplied from an equipped battery whose storage capacity is restricted.

Abstract: An optical disc drive equipped with a TLN signal generating apparatus is disclosed. The TLN signal generating apparatus includes a TLN signal generating circuit for generating a TLN signal (track loss signal) based on signals obtained from an optical pick-up; a digitizing circuit for digitizing the TLN signal by comparing it with a reference level; and a correction circuit for correcting the TLN signal so that it is accurately digitized by the digitizing circuit irrespective of an offset component which is a direct current component contained in the TLN signal.

Abstract: A method includes selecting a subset of predictive frequencies from a set of disc drive frequencies consisting essentially of operational driving frequencies in the disc drive and system resonance frequencies in the disc drive. Correlation constants are determined that correlate sound power to mechanical vibration magnitudes at each of the frequencies in the subset of predictive frequencies. The method further includes acquiring mechanical vibration data from the disc drive while operating the disc drive and determining predictive vibration magnitudes at each of the frequencies in the subset of predictive frequencies from the mechanical vibration data. Finally, the method includes determining an estimated acoustic sound power value for the disc drive from the determined correlation constants and the predictive vibration magnitudes. A testing system determines an estimated acoustic sound power value for a subject disc drive from predetermined correlation constants and vibration magnitudes.

Abstract: A method of adjusting the write speed of a CD drive includes writing data from a CD drive to a disk at a first speed. Then, if the absolute time in pregroove (ATIP) error rate of the compact disk at the first speed is larger than a corresponding first preset error allowance upper limit for the first speed, then the first speed is reduced. On the other hand, if the ATIP error rate of the compact disk at the first speed is smaller than the first preset error allowance upper limit, then data continues to be written from the CD drive to the disk at the same first speed. Thus, write failures can be avoided and the quality of the written data can be improved.

Abstract: The optical disk player is capable of correctly reading audio data from a damaged optical disk and forwarding reliable audio data to a host computer. In the optical disk player, a spindle motor rotates the optical disk. A servo processor controls revolution of the spindle motor. An optical pick-up reads audio data from the optical disk. A decoder decodes the audio data read by the optical pick-up. A buffer memory buffers the audio data decoded by the decoder. A CPU detects errors of reading audio data and controls the servo processor. The control means controls the revolution control means to make a data reading velocity slower if the control means detects any error of reading audio data.

Abstract: A disk drive servo system for eccentricity compensation and a method thereof includes an error detector detecting a position error between an actual position and a predetermined nominal reference position of a turntable actuator, a feedback unit generating and outputting a first control value to compensate for the position error received from the error detector, a learning controller calculating, storing, and outputting a second control value to compensate for eccentricity at one or more predetermined speeds of the disk drive, and a gain/phase adjustor providing gain and phase compensation information corresponding to the second control value of the learning controller according to frequency response characteristics of the turntable actuator at the one or more predetermined speeds.

Abstract: The present invention provides a disk driving apparatus which includes an interpolating edge circuit for generating an interpolating signal in accordance with a cycle of an edge detection signal, and a phase switching unit for performing phase switching by both the timing signal and the interpolating signal when a period for which the edge detection signal is normally generated reaches a predetermined value.

Abstract: An optical disk recording method comprising steps of a) performing recording onto the optical disk with a ZCLV method by using zone parameter storage means for storing at least one zone division time and CLV of each zone in a track formed on the optical disk, as zone parameters, for each of a plurality of recording modes and optical disk type determination means for determining the type of the optical disk before recording; b) performing optimization of the recording velocity by detecting, before recording, servo signal fluctuation by accessing the optical disk, by determining maximum recording velocity defined by the speed of a rotational motor rotating the optical disk, and by calculating a changing point of the recording velocity; and c) limiting the speed of the rotational motor, when the servo signal fluctuation at the surface of the optical disk exceeds a reference level and determining the relation between the zone division time and the CLV of each zone.

Abstract: When a recording condition judgement section (28) determines a recording condition of the recording of data onto a disk, and the recording is discontinued in response to the decision, a recording speed setting section (29) switches a recording speed to a speed one step slower than the previous recording speed. With this arrangement, when the recording condition is inferior, the recording is discontinued to thereby avoid a recording failure. Moreover, the recording speed is corrected stepwisely so that a disk adaptable recording speed can be set.

Abstract: There is provided an apparatus for compensating for an eccentricity of an optical disc, including a driver on which an optical disc is mounted for rotation, an optical head for emitting optical beams to the optical disc and receiving optical beams reflected from the optical disc, a mover to which the optical head is secured and which moves in a radius-wise direction of the optical disc, a track cross generating circuit which receives a track error signal from the optical disc and transmits a track cross pulse, and a controller which receives the track cross pulse to thereby determine an eccentricity of the optical disc in view of the optical beams reflected from the optical disc, and controls a rotational frequency of the optical disc in accordance with the thus determined eccentricity. The apparatus provides an advantage that an average transfer rate is increased for the long run.

Abstract: When a deviated gravity disc is reproduced at a higher rate with the disc reproducing apparatus, an excessive vibration is generated and this vibration gives adverse effect on the disc reproducing apparatus and peripheral components/apparatuses, and/or may represent an annoyance to a user. A vibration information detector for detecting vibration of the disc reproducing apparatus or a deviated gravity information detector for detecting amount of gravity deviation of disc is provided, and as a result of such detection of an imbalance (i.e., excessive vibration or mass eccentricity), and a reproducing rate switching control controls sets and limits the reproducing rate of the disc reproducing apparatus to a substitute speed which is lower or higher than a normal reproducing speed.

Abstract: A reproducing apparatus including a reading apparatus for reading signals recorded on a recording medium, a reproducing apparatus for reproducing data from read-out signals from the reading apparatus, an error detector for detecting an error in the data reproduced by the reproducing apparatus, a phase-synchronizing apparatus for synchronizing signals, for the reproducing apparatus, a characteristic changing apparatus for changing reproduction characteristics of the reproducing apparatus of loop characteristics of the phase-synchronizing apparatus, when the error detector detects an error on any one of a track on the recording medium, and a retry apparatus for retrying reading of a track on which the error is detected, under changed reproduction characteristics.

Abstract: Read data is given reproduction processing, including data correction, in synchronism with a bit clock. A disk with signals recorded thereon according to a constant linear velocity method is able to be rotated under control according to a constant angular velocity method. The rotation controller is set free from the control by the operation suspend controller. With this arrangement, the disk continues to rotate even when data writing to the buffer memory is suspended, and, upon resumption of a signal reading from the desk, signal processing is promptly carried out to a signal read from the disk, irrespective of the radial dimension of the point from which the signal was read on the disk.

Abstract: A servo control apparatus and method that adjust the allowable maximum rotation speed of an optical disk based upon the amount of disk axial vibration. The servo control apparatus in accordance with the present invention includes a driver for rotating the optical disk, a detector for detecting the amount of axial vibration of the optical disk, and a controller for controlling the rotation speed of the optical disk based upon the detected amount of disk axial vibration. The servo control apparatus and method in accordance with the present invention prevents data read error due to disk axial vibration by adjusting the allowable maximum disk rotation speed in consideration for the amount of disk axial vibration caused by imperfect disk manufacturing process, disk clamping error, or disk tilt.

Abstract: When a deviated gravity disc is reproduced at a higher rate with the disc reproducing apparatus, an excessive vibration is generated and this vibration gives adverse effect on the disc reproducing apparatus and peripheral components/apparatuses, and/or may represent an annoyance to a user. A vibration information detector for detecting vibration of the disc reproducing apparatus or a deviated gravity information detector for detecting amount of gravity deviation of disc is provided, and as a result of such detection of an imbalance (i.e., excessive vibration or mass eccentricity), and a reproducing rate switching control controls sets and limits the reproducing rate of the disc reproducing apparatus to a substitute speed which is lower or higher than a normal reproducing speed.

Abstract: A power saving system of an optical recording/reproducing apparatus is provided. The optical recording/reproducing apparatus includes a temporal memory which stores reproduced data or recording data in a cyclic data storage stage and from which the stored data is read out for reproduction or recording in a cyclic data readout stage following the data storage stage. The power saving system saves part of power consumed in the apparatus in the data storage stage in a record mode of operation and in the data readout stage in a reproduce mode of operation.

Abstract: Vibrations transferred to the outside are lessened and high performance against external vibrations and impact is maintained. Further, data is recorded and reproduced satisfactorily. A CD-ROM drive device is provided which is capable of reproducing data at a standard speed, a quadruple speed and a sextuple speed. When a disk is mounted to the CD-ROM drive device, TOC information is read in a playback state at the standard speed (ST1). Next, the disk is placed in a playback state at the sextuple speed and is set to a state held at a predetermined address position (ST2). It is distinguished using a tracking error signal, a control signal for a spindle motor, etc. whether the disk is either an eccentric disk or an unbalance disk (ST3). When the disk is found not to be either the eccentric disk or the unbalance disk, a playback speed is set to the sextuple speed. On the other hand, when the disk is found to be either the eccentric disk or the unbalance disk, the playback speed is set to the quadruple speed.

Abstract: A servo control system for a shock-proof disk player comprising a digital signal processor, a voltage-controlled oscillator, a reference clock generator, a clock mode changeover switch, a phase comparator for controlling a head-rotating spindle motor, and a bulk memory of a large capacity for storage of data, wherein the phase lock of a PLL at the time of a seek is switched on or off under control to thereby shorten the required seek time. The clock signal frequency is selectively changed in such a manner as to lock the PLL in accordance with the rotation rate, whereby the power consumption can be lowered. The bulk memory is used as a data buffer, and the servo system is controlled as the data are read out from the memory while the data quantity stored and left therein is detected, so that a reduction of the power consumption can be achieved with another advantage of enhancing the resistance against shock.

Abstract: A disk reading apparatus for reading data recorded on a disk medium is disclosed. The disk reading apparatus comprises a motor for rotating the disk medium, a vibration sensor section for detecting vibrations generating inside the disk reading apparatus and for converting the vibrations into a signal, a binarized signal generation section for extracting only a frequency component corresponding to the rotary speed of the disk medium from the signal outputted from the vibration sensor section, and for outputting a signal in which a binaraization is performed, a vibration judgement section for measuring a period of the binarized signal outputted from the binarized signal generation section and for outputting a vibration detection signal when the period of the binarized signal corresponds to the rotary speed of the disk medium, and a rotation control section for lowering the rotary speed of the disk medium when the vibration detection signal is inputted.

Abstract: An information reproducing apparatus is disclosed that comprises measuring means for measuring the intensity of a jitter of a signal read from an information record medium such as a disc, storing means for temporarily storing reproduced information at a first transfer rate, means for reading information stored in the storing means at a second transfer rate that is smaller than the first transfer rate, wherein the maximum speed of the information record medium is set up corresponding to the intensity of the jitter measured by the measuring means.

Abstract: CD-ROMS of poor quality, such as those having eccentric center holes or uneven weight distributions circumferentially, are easy to wobble or otherwise vibrate when driven at high speed, overloading tracking and focusing servos and inviting read errors and retries. Each CD-ROM on being loaded into a CD-ROM drive is therefore checked as to its quality in terms of the speed of rotation at which the disk drive motor gains a steady state on being started up at a full supply voltage. The poorer the disk quality, the lower is the steady state speed of motor rotation. A poor quality disk is read at four times the standard audio CD speed, an intermediate quality disk at eight times that speed, and a good quality disk at twelve times that speed.