Hitachi Global Storage Technologies Netherlands B.v.

Hgst Netherlands, B.v.

Jeffrey Joesph Dobbek

Kirk Hwang

David Robison Hall

Gregory Michael Frees

Daniel Jonathan Auerbach

A method and system are described for performing an arithmetic operation such as multiplication or division of a fixed point variable measured at runtime by a floating point constant known at compile-time. The floating point constant is converted into a mantissa and a base-2 exponent at compile-time. The mantissa and exponent are preferably combined into a single unit (a word) of memory. At runtime either single multiplication and accumulation or matrix multiplication and accumulation is preferably achieved by a microprocessor or DSP instruction designed to use the mantissa-exponent pairs stored in a word of memory. The microprocessor instruction multiplies a fixed point runtime variable x by the mantissa and the result is shifted to the right or left as indicated by the exponent, which is preferably a 2's complement number. The complete instruction sequence to perform the multiplication can be made reentrant and can be pipelined.

Method and system for performing calculations using fixed point microprocessor hardware

A method, apparatus and program storage device that provides a shift process with saturation for digital signal processor operations are disclosed. An instruction is generated for shifting an operand to either maximum or the minimum value depending on the bit of data input when saturation occurs. A saturation detection circuit is combined with an arithmetic shifter and a final decision multiplexor. The final decision multiplexor receives the output from the arithmetic shifter and the saturated value from the saturation circuit. When saturation is detected by the saturation detection circuit, the final decision multiplexor selects the saturate minimum or the saturate maximum depending on whether the MSB of the data in equals one or zero, respectively.

Method, apparatus and program storage device that provides a shift process with saturation for digital signal processor operations

A digital filter instruction and filter implementing the filter instruction are disclosed. The filter instruction synthesizes a digital filter and includes an instruction field, a tap length field, a coefficient address field, a data header address field, a clear accumulator bit and an update bit. The filter instruction a concise instruction format to significantly decrease memory required, allow for instruction pipelining without branch penalty, and uses a circular buffer for the data so the data address pointer is only needed to be updated for the next input sample. The filter instruction may be used to implement FIR or IIR filters by using the options of pre-clear accumulator or pre/post storing accumulator results.

Digital filter instruction and filter implementing the filter instruction

A method and apparatus for providing a processor based nested form polynomial engine are disclosed. A concise instruction format is provided to significantly decrease memory required and allow for instruction pipelining without branch penalty using a nested form polynomial engine. The instruction causing a processor to set coefficient and data address pointers for evaluating a polynomial, to load loading a coefficient and data operand into a coefficient register and a data register, respectively, to multiply the contents of the coefficient register and data register to produce a product, to add a next coefficient operand to the product to produce a sum, to provide the sum to an accumulator and to repeat the loading, multiplying, adding and providing until evaluation of the polynomial is complete.

Method and apparatus for providing a processor based nested form polynomial engine

Tilt between a head stack and its associated disk stack in a hard disk drive (HDD) is measured by determining the deviation of a target head from its expected position (based on the position of the current head) each time electrical contact is switched from the current head to a target head. A running average tilt value is stored and used to modify the logical seek distance used in a Rotational Position Optimization (RPO) algorithm to better order I/O requests in a queue. Also, the running average tilt value can be used by the servo to pre-position the target head before electrical contact is made with the target head, to improve speed of operation.

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Morgan Hill, CA, United States of America

Jeffrey Joesph Dobbek