Abstract: A floating point unit of an in-order-processor having a register array for storing a plurality of operands, a pipeline for executing floating point instructions with a plurality of stages, each stage having a stage register, data input registers (1A, 1B, 1C) for keeping operands to be processed. The data input registers form the first stage register of the pipeline. An input port loads operands from outside said floating point unit into one of said data input registers. A plurality of bypass-registers are provided, the input of which is connected to the input port, and the output of which is provided to the data input registers (1A, 1B, 1C), such that data propagating through the pipeline to be loaded into the register array can be immediately supplied to one or more particular data input registers (1A, 1B, 1C) from a respective bypass-register without a delay caused by additional pipeline stages to be propagated through.

Abstract: A two level branch history table (TLBHT) is substantially improved by providing a mechanism to prefetch entries from the very large second level branch history table (L2 BHT) into the active (very fast) first level branch history table (L1 BHT) before the processor uses them in the branch prediction process and at the same time prefetch cache misses into the instruction cache. The mechanism prefetches entries from the very large L2 BHT into the very fast L1 BHT before the processor uses them in the branch prediction process. A TLBHT is successful because it can prefetch branch entries into the L1 BHT sufficiently ahead of the time the entry is needed. This feature of the TLBHT is also used to prefetch instructions into the cache ahead of their use. In fact, the timeliness of the prefetches produced by the TLBHT can be used to remove most of the cycle time penalty incurred by cache misses.

Abstract: In the world of high speed communications where the use of return-to-zero modulation format is advantageous, there is a need for being able to exert electrical control, in a relatively simple manner, over the duty cycle of the optical pulses being generated without the undesirable effects of chirp, whilst providing good extinction between pulses. The invention proposes an optical pulse generator and methods of generating and shaping optical pulses using an arrangement of cascaded Mach-Zehnder type interferometers. The pulse generator has a signal generator that produces sinusoidal electrical modulation signals for application to the electrical inputs of cascaded Mach-Zehnder type interferometers. The first Mach-Zehnder type interferometer in the series is responsive to the sinusoidal electrical modulation signal being applied, to generate a series of optical pulses having controllable chirp.

Abstract: The optical modulator comprising an optical input signal waveguide, first and second interferometric waveguide arms, a modulated output signal waveguide, a splitter for dividing the input signal between the first and second arms, and a combiner for recombining the signals, transmitted along each of the first and second arms into the output signal waveguide. The first and second electrodes each of a segmented structure having a plurality of elements each extending from a respective one of the first and second electrodes and each terminating at position adjacent a length of corresponding one of the first and second arms wherein only a proportion of the elements terminate at positions such as to have an electro-optic effect on a signal transmitted through the corresponding one of the arms. Thus, only proportion of the elements are in active in the sense that only they induce a phase shift in the signal transmitted through the respective one of the arms.

Abstract: A suspension fork for caster wheels providing shock absorption, comfort and safety while maintaining the original castering characteristics. A fork supporting a wheel on an axle is allowed to pivot about a second axle or pin located at the opposite end of the fork, forward and above the trailing wheel. The forward pivot is housed inside an upper block, which acts as a mounting fixture to the desired vehicle. A stem bolt protrudes from the upper block into the vehicle's caster housing containing bearings providing sideways rotation for steering purposes. The pivoting action of the fork and wheel about the upper block is controlled by a spring/dampener of polymer seated between the two blocks. Rigid tabs or mechanical lock outs limit the range of fork pivot and capture the elastomeric material until the forward pin is removed. Standardized axle and stem bolt dimensions allow the suspension caster to readily replace a conventional rigid caster fork.

Abstract: A computer processor floating point processor six cycle pipeline system where instruction text is fetched prior to the first cycle and decoded during the first cycle for the fetched particular instruction and the base (B) and index (X) register values are read for use in address generation. RXE Instructions are of the RX-type but extended by placing the extension of the operation code beyond the first four bytes of the instruction format and to assign the operation codes in such a way that the machine may determine the exact format from the first 8 bits of the operation code alone.

Abstract: A computer processor system having a floating point processor for instructions which are processed in a six cycle pipeline, in which prior to the first cycle of the pipeline an instruction text is fetched, and during the first cycle for the fetched particular instruction it is decoded and the base (B) and index (X) register values are read for use in address generation. Instructions of the RX-type are extended by placing the extension of the operation code beyond the first four bytes of the instruction format and to assign the operation codes in such a way that the machine may determine from the first 8 bits of the operation code alone, the exact format of the instruction. Instructions formats include the ESA/390 instructions SS, RR; RX; S; RRE; RI: and the new RXE instructions. where instructions of the RXE format have their R.sub.1, X.sub.2, B.sub.2, and D.sub.

Abstract: Preprocessing emulation methods utilizing search argument controls for a template routine address table in a target computing system. Target routines are stored in a target computing system for emulating incompatible instructions of an incompatible architecture which need not be recognized by the architecture of the target computing system. Preprocessing of template routines is preferrably executed on an Auxiliary Emulation Processor (AEP) which may access and patch (modify) some or all of the target instructions in any selected target routine and send them through a queue to a target processor for execution. Execution of the target routines on a target processor emulates the execution of incompatible instructions in an incompatible program in the incompatible architecture.

Abstract: An IEEE 754 standard floating point multiply instruction for binary extended precision format can be executed with a quad word format on an S/390 process. The multiplication calculation multiplies each partition by each other. In the multiplication calculation process dataflow process of either operand is a denormalized number, they are normalized at a stage which creates an expanded exponent range of one more bit, and the calculation continues to a parallel path multiplexor stage, but if neither operand is denormalized then the exponent of the number is expended and the calculation splits into four parallel paths, wherein two operand's sign bits are processed in a sign calculation block stage, the operands' two 16 bit binary exponents are processed by an exponent conversion block stage, and a partition multiplicand significand block stage receives a 113 bit multiplicand significand input for a fourth path.

Abstract: A floating point unit has a control unit, a data input register and a write stage register from which an instruction is transferred from the floating point unit to a storage unit. The floating point unit typically has multiple pipeline stages for arithmetic computation, a normalization stage, and a rounding stage, each of which pipeline stages may during processing of a stream of instructions contain a separate instruction. The stages are connected in an ordered manner such that the processing of instructions occurs in the pipeline. An active instruction is a "stalled" instruction within a pipeline when forward progress is not permitted to advance to a new stage in the pipeline because data needed is not available for a prior instruction creating a data dependency.

Abstract: IEEE compliant floating point unit mechanism allows variability in the execution of floating point operations according to the IEEE 754 standard and allowing variability of the standard to co-exist in hardware or in the combination of hardware and millicode. The FPU has a detector of special conditions which dynamically detects an event that the hardware execution of an IEEE compliant Binary Floating Point instruction will require millicode emulation. The complete set of events which millicode may emulate are predetermined early in the design process of the hardware. An exception handling unit assist millicode emulation by trapping the result of an exceptional condition without invoking the trap handler. When an exceptional condition is detected during execution, the IEEE 754 standard requires two different actions under control of a mask bit. If the mask bit is on, the result is written into an FPR and the trap handler is invoked.

Abstract: There is a unique partitioning problem in determining how to execute the floating point multiply instruction defined by IEEE 754 standard for the quad word format on a S/390 processor. Several manufacturers including IBM and HP define the binary quad word format to have a 113 bit significand. IBM S/390 hexadecimal long floating point format has a 56 bit significand and most S/390 floating point units only contain a long format multiplier. Quad word format multiplication must be executed as a series of several long precision multiplications and extended precision or long precision additions. The S/390 hexadecimal quad word format is easier to implement than binary format since it has a 112 bit significand and can easily be partitioned into two 56 bit parts. But a 113 bit significand would just exceed two partitions and require a third.

Abstract: Provides a program translation and execution method which stores target routines (for execution by a target processor) corresponding to incompatible instructions, interruptions and authorizations of an incompatible program written for execution on another computer system built to a computer architecture incompatible with the architecture of the target processor's computer system. The disclosed process allows the target processor to emulate incompatible acts expected in the operation of an incompatible program when the target processor itself is incapable of performing the emulated acts. Each of the instructions, interruptions and authorizations found in the incompatible programs has one or more corresponding target routines, any of which may need to be preprocessed before it can precisely emulate the execution results required by the incompatible architecture.

Abstract: A method and system for processing instructions in a floating point unit for executing denormalized numbers in floating point pipeline via serializing uses an instruction unit and having a control unit and a pipelined data flow unit, a shifter and a rounding unit. The floating point unit has an external feedback path for providing intermediate result data from said rounding unit to an input of the pipelined data flow unit to reuse the pipeline for denormalization by passing intermediate results in the pipeline which have a denormalized condition computed after the exponent calculation of the shifting circuit directly from the rounding unit to the top of the dataflow in the pipeline via an external feedback path. The pipelined has two paths which are selected based on the presence of other instructions in the pipeline. If no other instructions are in the pipeline a first path is taken which uses the external feedback path from the rounding unit back into the top of the dataflow.

Abstract: A method and system which provides exactly rounded division and square root results for a designated rounding mode independently of a remainder, or equivalent calculation of the relationship between the remainder and zero, for predetermined combinations of the rounding mode and the guard digit of an estimate that has several more bits of precision than the exactly rounded result, and has an error tolerance magnitude less than the weight of the least significant bit of the estimate. The estimate is generated in accordance with a quadratically converging division or square root algorithm. The method and system is described in connection with IEEE 754-1985 and IBM S/390 binary floating point architectures.

Abstract: A system implementing a methodology for determining the exponent in parallel with determining the fractional shift during normalization according to partitioning the exponent into partial exponent groups according to the fractional shift data flow, determining all possible partial exponent values for each partial exponent group according to the fractional data flow, and providing the exponent by selectively combining possible partial exponents from each partial exponent group according to the fractional data flow. There is also provided a system implementing a methodology for generating the sticky bit during normalization. Sticky bit information is precalculated and multiplexed according to the fractional dataflow. In an embodiment of the invention, group sticky signals are calculated in tree form, each group sticky having a number of possible sticky bits corresponding to the shift increment amount of the multiplexing.

Abstract: A system implementing a methodology for determining the exponent in parallel with determining the fractional shift during normalization according to partitioning the exponent into partial exponent groups according to the fractional shift data flow, determining all possible partial exponent values for each partial exponent group according to the fractional data flow, and providing the exponent by selectively combining possible partial exponents from each partial exponent group according to the fractional data flow. There is also provided a system implementing a methodology for generating the sticky bit during normalization. Sticky bit information is precalculated and multiplexed according to the fractional dataflow. In an embodiment of the invention, group sticky signals are calculated in tree form, each group sticky having a number of possible sticky bits corresponding to the shift increment amount of the multiplexing.

Abstract: A system implementing a methodology for determining the exponent in parallel with determining the fractional shift during normalization according to partitioning the exponent into partial exponent groups according to the fractional shift data flow, determining all possible partial exponent values for each partial exponent group according to the fractional data flow, and providing the exponent by selectively combining possible partial exponents from each partial exponent group according to the fractional data flow. There is also provided a system implementing a methodology for generating the sticky bit during normalization. Sticky bit information is precalculated and multiplexed according to the fractional dataflow. In an embodiment of the invention, group sticky signals are calculated in tree form, each group sticky having a number of possible sticky bits corresponding to the shift increment amount of the multiplexing.

Abstract: A method and system which provides exactly rounded division and square root results for a designated rounding mode independently of a remainder, or equivalent calculation of the relationship between the remainder and zero, for predetermined combinations of the rounding mode and the least significant bit of an estimate that has one more bit of precision than the exactly rounded result, and has an error tolerance magnitude less than the weight of the least significant bit of the estimate. The estimate is generated in accordance with a quadratically converging division or square root algorithm. The method and system is described in connection with IEEE 754-1985 and IBM S/390 binary floating point architectures.