Abstract: A magnetic disc storage system includes a rotating magnetic disc and a read/write transducer positioned proximate a recording surface of the magnetic disc for reading and writing information on the recording surface. Data stored on the recording surface is altered based upon the address of the data. During readback, a pseudorandom number generator receives a desired address as a seed input and provides a pseudorandom number output. An XOR gate provides an XOR output in response to the pseudorandom number output and the readback signal from the read/write transducer. An error detection circuit provides a decoded data output and an error flag output in response to the XOR output. An error during readback indicated by the error flag output is indicative of an incorrect address of the readback signal in comparison to the desired address. During a write operation, data is provided to an error detector encoder circuit which provides an encoded data output to an XOR gate.

Abstract: A disc controller services a host "read" command, without intervention by the disc controller's microcontroller, if the requested data is found in the disc controller's cache. The disc controller stores at least one cache entry. Each cache entry includes an address, a logical Bit, a valid Bit and a set of four buffer parameters: upper limit address, base address, pointer to the sector count and sector count. Each host command is decoded by the disc controller, and if the command is a "read" command the address in the cache entry is compared against the address in the host command. If the addresses match and the cache entry address is marked as being valid by its Valid bit, a "cache hit" signal is generated and the disc controller starts transferring the data requested by the host without waiting for the disc controller's microprocessor to process the host command.