Abstract: A disk drive array controller and method carries out disk drive data transfers not only concurrently but also synchronously with respect to all of the drives in the array. For synchronous operation, only a single-channel DMA is required to manage the buffer memory. A single, common strobe is coupled to all of the drives for synchronous read and write operations, thereby reducing controller complexity and pin count. A ring-structure drive data bus together with double buffering techniques allows use of a single, common shift clock instead of a series of staggered strobes as required in prior art for multiplexing/demultiplexing buffer memory data, again providing for reduced controller complexity and pin count in a preferred integrated circuit embodiment of the new disk array controller. Methods and circuitry also are disclosed for generating and storing redundant data (e.g. “check” or parity data) “on the fly” during a write operation to a RAID array.

Abstract: A disk drive array controller and method carries out disk drive data transfers not only concurrently but also synchronously with respect to all of the drives in the array. For synchronous operation, only a single-channel DMA is required to manage the buffer memory. A single, common strobe is coupled to all of the drives for synchronous read and write operations, thereby reducing controller complexity and pin count. A ring-structure drive data bus together with double suffering techniques allows use of a single, common shift clock instead of a series of staggered strobes a required in prior art for multiplexing/demultiplexing buffer memory data, again providing for reduced controller complexity and pin count in a preferred integrated circuit embodiment of the new disk array controller. Methods and circuitry also are disclosed for generating and storing redundant data (e.g. "check" or parity date) "on the fly" during a write operation to a RAID array.

Abstract: Rate 24/25 modulation encoding methods and apparatus improve efficiency in a PRML magnetic recording channel. The rate 24/25 code word uses rate 8/9 RLL encoding of one byte of user data, combined with interleaved unencoded bytes to achieve improved code rates with reasonable global run length constraint. Use of the the rate 8/9 RLL (0,3) subcode results in a rate 24/25 RLL (0,11) code, while a rate 8/9 (0,6/5) subcode results in a rate 24/25 RLL (0,14/13) code.

Abstract: Determining a micro-jog parameter in a disk drive that employs a magneto-resistive (MR) transducer head assembly and a partial response (PRML) detector includes improved accuracy in measuring on-track signal strength by use of a matched filter technique. The matched filter includes circuitry for emulating a partial response signal expected to be produced by a selected test bit pattern prerecorded on the selected track. The matched filtering technique provides improved accuracy in measuring the detected signal strength as it provides an extremely narrow digital filter focused on the test bit pattern frequency. Improved determination of the micro-jog distance further includes measuring interference from adjacent tracks, the best error rate being achieved at micro-jog positions intermediate the maximum on-track signal strength and the minimum off-track interference. A novel digital detector for accurately measuring adjacent track interference also is disclosed.

Abstract: Computer-controlled test and measurement systems, including resources having multiple states and resources having multiple inputs, are modeled as data flow diagrams of topologically interconnected resources. A set of "tasks" are defined for changing the states of multiple-state resources and causing software resources to produce output data. Methods and apparatus, including internal and external task ordering rules, are provided to automatically interleave such tasks and implement input-ordering restrictions. Thereby, a sequence of tasks is produced to control the systems so as to assure valid data collection and protect physical resources from abuse. Data structures are illustrated for implementing the invention in an object-oriented programming environment.

Abstract: A method for typographic design of a printed document utilizing typographical parameters designed by an expert typographer is provided. A standard body of text is executed in a standard font and a selected format by an expert design typographer to provide maximized readability of the standard body of text and to determine a set of reference parameters associated with that selected format. Utilizing the reference parameters in a computer program, an unskilled user may then execute a desired body of text in a desired font in the selected format to produce a printed document having substantially equal readability. The program allows a reader to switch between typefaces to produce printed documents having substantially equal copyfit in different typefaces.