International Business Machines Corporation

Advanced Micro Devices Corporation

Michael Thomas Dibrino

Faraydon O Karim

George McNeil Lattimore

Dwain Alan Hicks

Michael T Clark

Kimming K So

David M Wu

Jelena Ilic

Syed Faisal Ahmed

Hanaa Youssef

In an embodiment, a microcode unit for a processor is contemplated. The microcode unit comprises a microcode memory storing a plurality of microcode routines executable by the processor, wherein each microcode routine comprises two or more microcode operations. Coupled to the microcode memory, the sequence control unit is configured to control reading microcode operations from the microcode memory to be issued for execution by the processor. The sequence control unit is configured to stall issuance of microcode operations forming a body of a loop in a first routine of the plurality of microcode routines until a loop counter value that indicates a number of iterations of the loop is received by the sequence control unit.

Precise counter hardware for microcode loops

Presented is a &ldquo;high-order&rdquo; Leading Zeros Anticipator or LZA circuit and specifically a five-input LZA. The prior-art two-input LZA circuit is part of almost all high-performance floating-point units or FPUs. The advantages of a high-order LZA (such as five-input) is that the LZA function may be started and finished sooner in the floating point pipeline, and therefore allows more time for other functions in the pipeline. Therefore, a high-order LZA, such as five-input LZA, may be faster than the prior art two-input LZA designs. Thus, speeding up the LZA function in a floating point pipeline may significantly increase the speed in which the overall floating-point unit may operate as compared to the prior-art two input LZA designs and may additionally inspire new floating-point michroarchitectures which may yield further performance gains.

Floating point pipeline with a leading zeros anticipator circuit

An apparatus for generating an end-around carry to an end-around carry adder in a floating-point pipeline within a computer system is disclosed. The apparatus for generating an end-around carry includes a shift-comparison logic circuit, a sign-comparison circuit, and a logic gate. The shift-comparison logic circuit produces a shift-count signal and the sign-comparison logic circuit produces an effective operation signal. Coupled to the shift-comparison logic circuit and the sign-comparison logic circuit, the logic gate combines the shift-count signal and the effective operation signal with a carry-out signal generated by an end-around carry adder to provide an end-around carry signal for the end-around carry adder.

Method and apparatus for generating an end-around carry in a

A method and system for modeling the behavior of a circuit are disclosed. A list specifying a plurality of transistors within the circuit and interconnections between the plurality of transistors is provided. Each fan node within the circuit is identified, where a fan node is defined as a point of interconnection between two or more of the plurality of transistors from which multiple nonredundant current paths to power, ground, or an input of the circuit exist. A fan node equation set is constructed that expresses a logical state of each fan node of the circuit in response to various transistor gate signal states. In addition, an output node equation is constructed that expresses a logical state of an output node of the circuit in terms of selected fan node logical states and specified transistor gate signal states. In response to receipt of a set of states of inputs to the circuit, a logical state of the output node is determined utilizing the fan node equation set and the output equation in order to model behavior of the circuit.

Method and system for modeling the behavior of a circuit

A high performance shared cache is provided to support multiprocessor systems and allow maximum parallelism in accessing the cache by the processors, servicing one processor request in each machine cycle, reducing system response time and increasing system throughput. The shared cache of the present invention uses the additional performance optimization techniques of pipelining cache operations (loads and stores) and burst-mode data accesses. By including built-in pipeline stages, the cache is enabled to service one request every machine cycle from any processing element. This contributes to reduction in the system response time as well as the throughput. With regard to the burst-mode data accesses, the widest possible data out of the cache can be stored to, and retrieved from, the cache by one cache access operation. One portion of the data is held in logic in the cache (on the chip), while another portion (corresponding to the system bus width) gets transferred to the requesting element (processor or memory) in one cycle. The held portion of the data can then be transferred in the following machine cycle.

Multiprocessor system with shared cache and data input/output circuitry

A system and method for selecting a processor to service interrupts in a multiprocessor system with processor individualized interrupt priority states. The interrupt priority information associated with the various processors is bit serially compared to select one or more processors of lowest interrupt priority status, Processor individualized identification information is then compared to reconcile when multiple processors have an identical interrupt priority level, The outcome is stored and immediately available for managing interrupts generated by I/O devices, In a preferred arrangement, the interrupt priority status of the selected processor is confirmed immediately before processing the service requests to compensate for any changes occurring during the period of the bit serial comparison.

Apparatus and method for managing interrupts in a multiprocessor system

The invention is a system and method for providing a breakpoint exception at any predetermined instruction address in a processor system of the type including an integrated circuit microprocessor and an instruction cache and memory management unit (CMMU) where code addresses are sent to the instruction CMMU and the instruction CMMU returns with code instructions and returns with a FAULT code reply signal when there is no reply code, and wherein an exception is forced in the microprocessor in response to the FAULT code reply signal. The system comprises at least one breakpoint register for storing a predetermined breakpoint address, a means for comparing the code addresses which are sent to the CMMU with the predetermined breakpoint address in the breakpoint register and for generating a match signal when equivalent addresses are detected, and a means coupled to the CMMU and responsive to said match signal for causing said CMMU to issue a FAULT code reply signal, whereby an exception is forced in the microprocessor. The system is especially suitable for use with the Motorola MC88100 processor and MC88200 CMMU.

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Austin, TX, United States of America

Michael Thomas Dibrino