Abstract: A cache for improving access to optical media includes a primary cache comprising RAM and a secondary cache comprising a portion of hard disk memory. Multiple aspects of the invention are defined: (1) Cache data discrimination: Discrimination methodology is implemented for determining when data should not be cached. Under certain conditions, caching of data is less likely to improve access time. (e.g., when the transfer rate is already exceeding a critical sustained throughput rate; when an estimated time to complete a CD-ROM data request is within a specific percentage of the estimated time to complete a hard drive disk request). (2) Secondary cache fragmentation avoidance: To keep the access time to secondary cache faster than the access time to the optical media, fragmentation of the secondary cache (i.e., hard disk) is minimized.

Abstract: A method and apparatus for error detection and correction in the storage and retrieval of digital data on magnetic storage systems includes converting the digital data into analog waveforms, multiplexing the analog waveforms with reference values and storing same as a data stream, demultiplexing the reference values from the data stream and using the retrieved reference values to detect and reduce distortion or other errors in the data stream. Assignment of data to analog waveforms includes option of assigning arbitrary quantities of data to a compact analog waveform representation. Analog errors may be detected and corrected statistically, while digital errors may be detected and corrected using standard signal processing techniques.