Electrical computers and digital processing systems: processing – Processing architecture – Superscalar
Reexamination Certificate
1999-12-20
2001-04-17
Pan, Daniel H. (Department: 2183)
Electrical computers and digital processing systems: processing
Processing architecture
Superscalar
C712S024000, C712S226000, C712S236000, C712S238000
Reexamination Certificate
active
06219778
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
The subject matter of the present application is related to that of co-pending U.S. patent application Ser. No. 08/881,958 now U.S. Pat. No. 6,094,719, identified as Docket No. P2345/37178.830071.000 for AN APPARATUS FOR HANDLING ALIASED FLOATING-POINT REGISTERS IN AN OUT-OF-ORDER PROCESSOR filed concurrently herewith by Ramesh Panwar; Ser. No. 08/881,926, now U.S. Pat. No. 5,981,594, identified as Docket No. P2348/37178.830073.000 for AN APPARATUS FOR NON-INTRUSIVE CACHE FILLS AND HANDLING OF LOAD MISSES filed concurrently herewith by Ramesh Panwar and Ricky C. Hetherington; Ser. No. 08/881,908, now U.S. Pat. No. 6,098,165 identified as Docket No. P2349/37178.830074.000 for AN APPARATUS FOR HANDLING COMPLEX INSTRUCTIONS IN AN OUT-OF-ORDER PROCESSOR filed concurrently herewith by Ramesh Panwar and Dani Y. Dakhil; Ser. No. 08/882,173, now U.S. Pat. No. 5,898,853 identified as Docket No. P2350/37178.830075.000 for AN APPARATUS FOR ENFORCING TRUE DEPENDENCIES IN AN OUT-OF-ORDER PROCESSOR filed concurrently herewith by Ramesh Panwar and Dani Y. Dakhil; Ser. No. 08/881,145 identified as Docket No. P2351/37178.830076.000 for APPARATUS FOR DYNAMICALLY RECONFIGURING A PROCESSOR filed concurrently herewith by Ramesh Panwar and Ricky C. Hetherington; Ser. No. 08/881,732, now U.S. Pat. No. 6,058,466 as Docket No. P2353/37178.830077.000 for APPARATUS FOR ENSURING FAIRNESS OF SHARED EXECUTION RESOURCES AMONGST MULTIPLE PROCESSES EXECUTING ON A SINGLE PROCESSOR filed concurrently herewith by Ramesh Panwar and Joseph I. Chamdani; Ser. No. 08/882,175, now U.S. Pat. No. 6,055,616, identified as Docket No. P2355/37178.830078.000 for SYSTEM FOR EFFICIENT IMPLEMENTATION OF MULTI-PORTED LOGIC FIFO STRUCTURES IN A PROCESSOR filed concurrently herewith by Ramesh Panwar; Ser. No. 08/882,311, now U.S. Pat. No. 6,058,472, identified as Docket No. P2365/37178.830080.000 for AN APPARATUS FOR MAINTAINING PROGRAM CORRECTNESS WHILE ALLOWING LOADS TO BE BOOSTED PAST STORES IN AN OUT-OF-ORDER MACHINE filed concurrently herewith by Ramesh Panwar, P. K. Chidambaran and Ricky C. Hetherington; Ser. No. 08/881,731, now U.S. Pat. No. 6,144,982, identified as Docket No. P2369/37178.830081.000 for APPARATUS FOR TRACKING PIPELINE RESOURCES IN A SUPERSCALAR PROCESSOR filed concurrently herewith by Ramesh Panwar; Ser. No. 08/882,525, now U.S. Pat. No. 6,006,326, identified as Docket No. P2370/37178.830082.000 for AN APPARATUS FOR RESTRAINING OVER-EAGER LOAD BOOSTING IN AN OUT-OF-ORDER MACHINE filed concurrently herewith by Ramesh Panwar and Ricky C. Hetherington; Ser. No. 08/882,220, now U.S. Pat. No. 5,941,977, as Docket No. P2371/37178.830083.000 for AN APPARATUS FOR HANDLING REGISTER WINDOWS IN AN OUT-OF-ORDER PROCESSOR filed concurrently herewith by Ramesh Panwar and Dani Y. Dakhil; Ser. No. 08/881,847 now U.S. Pat. No. 6,049,868, identified as Docket No. P2372/37178.830084.000 for AN APPARATUS FOR DELIVERING PRECISE TRAPS AND INTERRUPTS IN AN OUT-OF-ORDER PROCESSOR filed concurrently herewith by Ramesh Panwar; Ser. No. 08/881,728, now U.S. Pat. No. 6,154,815 identified as Docket No. P2398/37178.830085.000 for NON-BLOCKING HIERARCHICAL CACHE THROTTLE filed concurrently herewith by Ricky C. Hetherington and Thomas M. Wicki; Ser. No. 08/881,727 now U.S. Pat. No. 6,148,371, identified as Docket No. P2406/37178.830086.000 for NON-THRASHABLE NON-BLOCKING HIERARCHICAL CACHE filed concurrently herewith by Ricky C. Hetherington, Sharad Mehrotra and. Ramesh Panwar; Ser. No. 08/881,065, now U.S. Pat. No. 6,081,873, identified as Docket No. P2408/37178.830087.000 for IN-LINE BANK CONFLICT DETECTION AND RESOLUTION IN A MULTI-PORTED NON-BLOCKING CACHE filed concurrently herewith by Ricky C. Hetherington, Sharad Mehrotra and Ramesh Panwar; and Ser. No. 08/882,613 now U.S. Pat. No. 5,948,106, identified as Docket No. P2434/37178.830088.000 for SYSTEM FOR THERMAL OVERLOAD DETECTION AND PREVENTION FOR AN INTEGRATED CIRCUIT PROCESSOR filed concurrently herewith by Ricky C. Hetherington and Ramesh Panwar, the disclosures of which applications are herein incorporated by this reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to microprocessors and, more particularly, to a system, method, and microprocessor architecture providing precise state updates in an out-of-order machine.
2. Relevant Background
Early computer processors (also called microprocessors) included a central processing unit or instruction execution unit that executed only one instruction at a time. As used herein the term processor includes complex instruction set computers (CISC), reduced instruction set computers (RISC) and hybrids. In response to the need for improved performance several techniques have been used to extend the capabilities of these early processors including pipelining, superpipelining, superscaling, speculative instruction execution, and out-of-order instruction execution.
Pipelined architectures break the execution of instructions into a number of stages where each stage corresponds to one step in the execution of the instruction. Pipelined designs increase the rate at which instructions can be executed by allowing a new instruction to begin execution before a previous instruction is finished executing. Pipelined architectures have been extended to “superpipelined” or “extended pipeline” architectures where each execution pipeline is broken down into even smaller stages (i.e., microinstruction granularity is increased). Superpipelining increases the number of instructions that can be executed in the pipeline at any given time.
“Superscalar” processors generally refer to a class of microprocessor architectures that include multiple pipelines that process instructions in parallel. Superscalar processors typically execute more than one instruction per clock cycle, on average. Superscalar processors allow parallel instruction execution in two or more instruction execution pipelines. The number of instructions that may be processed is increased due to parallel execution. Each of the execution pipelines may have differing number of stages. Some of the pipelines may be optimized for specialized functions such as integer operations or floating point operations, and in some cases execution pipelines are optimized for processing graphic, multimedia, or complex math instructions.
The goal of superscalar and superpipeline processors is to execute multiple instructions per cycle (IPC). Instruction-level parallelism (ILP) available in programs can be exploited to realize this goal, however, this potential parallelism requires that instructions be dispatched for execution at a sufficient rate. Conditional branching instructions create a problem for instruction fetching because the instruction fetch unit (IFU) cannot know with certainty which instructions to fetch until the conditional branch instruction is resolved. Also, when a branch is detected, the target address of the instructions following the branch must be predicted to supply those instructions for execution.
Recent processor architectures use a branch prediction unit to predict the outcome of branch instructions allowing the fetch unit to fetch subsequent instructions according to the predicted outcome. Branch prediction techniques are known that can predict branch outcomes with greater than 95% accuracy. These instructions are “speculatively executed” to allow the processor to make forward progress during the time the branch instruction is resolved. When the prediction is correct, the results of the speculative execution can be used as correct results, greatly improving processor speed and efficiency. When the prediction is incorrect, the completely or partially executed instructions must be flushed from the processor and execution of the correct branch initiated.
Early processors executed instructions in an order determined by the compiled machine-language program running on the processor and so are referred to as “in-order” or “sequential” processors. In superscalar processors multiple pipelines can simul
Panwar Ramesh
Prabhu Arjun
Gunnison, McKay & Hodgson LLP
McKay Philip
Nguyen Dzung C.
Pan Daniel H.
Sun Microsystems Inc.
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