Tools For Testing Of CMO's Processor Objectives

Tools For Testing Of CMO S Processorobjective

This project involves developing a tool to generate random instruction sequences for the hardware testing of a single-issue pipelined microprocessor, specifically focusing on a subset of an ISA supported by Simplescalar, such as ARM or PISA (MIPS-like). The goal is to create an assembly-level instruction sequence generator capable of producing test cases that can evaluate processor behavior, particularly in the presence of hazards and other pipeline phenomena. The project encompasses understanding assembly sequence creation, simulation, ISA description management, random sequence generation, hazard detection, and testing through simulation with Simplescalar.

Paper For Above instruction

Designing and implementing a robust testing framework for CMOS processor verification is crucial for validating processor functionality, detecting pipeline hazards, and ensuring correctness against architectural specifications. The core objective of this project is to develop an instruction sequence generator, capable of producing random, valid assembly instruction sequences, which can be used to test a simplified, single-issue pipelined microprocessor modeled in the Simplescalar simulator. This tool aims to facilitate systematic hardware testing by automating test case generation, hazard detection, and verification against known golden outputs, thereby enhancing the reliability of processor designs.

The first step in realizing this project involves familiarizing oneself with assembly programming, including writing, compiling, and simulating assembly sequences within the chosen ISA, such as ARM or PISA. Developing competence in this domain ensures that the generated sequences are syntactically and semantically valid, reducing the possibility of illegal instruction generation during test sequence creation. One key aspect is to write five assembly sequences, including data hazard scenarios—particularly RAW (Read After Write), WAW (Write After Write), and WAR (Write After Read)—that can be tested on Simplescalar. Notably, one sequence should perform an arithmetic mean calculation, serving as a benchmark test case, it will be scrutinized to verify hazard detection and instruction correctness in the pipeline.

To facilitate flexible and extendable testing, the tool must support a modular machine description file that defines the ISA encoding, typically via an include file. This modularity permits easy updates or replacements of the ISA description, enabling testing across different instruction sets without rewiring the entire tool. The sequence generator should accept user input for desired test length and generate instruction sequences accordingly, ensuring syntactic correctness in terms of instruction formats and register use.

Generating valid instruction sequences involves critical constraints, such as preventing branch instructions from exceeding their range limits, managing address calculation for load/store instructions if included, and avoiding illegal or unsupported opcodes. Early consideration of these constraints guarantees generated sequences are executable, reducing the need for extensive post-generation validation. If the tool supports machine code generation directly, detection and filtering of illegal instructions—such as reserved opcodes—become imperative to prevent simulation errors.

One significant feature of the testing tool is hazard detection and counting. The generator must identify and count static data hazards—RAW, WAW, WAR—in the generated instruction sequences. This hazard analysis aids in evaluating the impact of instruction scheduling and pipeline design. The count must be static, not runtime, to analyze the potential hazards embedded in the sequences before execution.

The testing process involves integrating the generated sequences into Simplescalar for simulation. For each generated sequence, verification is conducted by comparing the final processor state—registers and memory—with expected 'golden' results. Automating this verification can significantly improve efficiency, enabling batch testing across multiple sequences. Both the reference (golden) and the tested processor configurations should be modeled within Simplescalar, with the latter altered to reflect different pipeline or architectural features. This setup enables testing the sequences against multiple processor configurations, revealing discrepancies that could indicate design flaws or pipeline misimplementations.

Performing comparative simulation requires creating two processor configurations within Simplescalar, modifying one architectural feature in the second. Running the instruction sequences on both configurations allows for differential analysis, highlighting issues that may arise due to pipeline modifications, such as changes in hazard handling or instruction scheduling. Sequences deliberately designed to detect these differences are invaluable as stress tests for pipeline robustness. The entire process should be automated: sequence generation, simulation execution, output comparison, and hazard counting, culminating in a comprehensive report documenting methodology, results, and insights.

Essential tools include the Simplescalar simulator, a C/C++ compiler like GCC tailored for the target ISA, and scripting interfaces to automate sequence generation and testing. The project output should include a well-documented source code repository, a concise project report (less than three pages), and demonstration of the tool's capabilities through simulation results. Overall, this approach enables systematic testing of the CMOS processor's pipeline, hazard management, and correctness, contributing valuable insights into processor design validation and potential improvements.

References

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