Pipelined Microprocessor

Concept

A pipelined microprocessor partitions instruction execution into stages separated by pipeline registers so multiple instructions can be in flight at once. In the Y86-64 PIPE design described in the evidence, a five-stage pipeline uses fetch, decode, execute, memory, and writeback-style computation, with extra control logic and data paths to handle hazards, stalls, bubbles, forwarding, and branch mispredictions.

First seen 5/26/2026

Last seen 5/26/2026

Evidence 5 chunks

Wiki v1

WIKI

Overview

A pipelined microprocessor is illustrated by the Y86-64 PIPE implementation, a five-stage pipeline that implements the Y86-64 instruction set. PIPE is structurally similar to the sequential SEQ processor: both partition computation into similar stages and use the same set of functional blocks. The key difference is that PIPE adds state elements in the form of pipeline registers, enabling up to five instructions to flow through the pipeline simultaneously, each in a different stage. [C1]

Pipeline structure

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NEIGHBORHOOD

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RELATIONSHIPS

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UCLID5 ← evaluates 100% 1e

UCLID5 is used to verify pipelined microprocessor designs by modeling and checking their correctness.

LINKED ENTITIES

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Burch-Dill Correspondence Checking verification_method The evidence states that the verification script describes the steps required to carry out Burch-Dill correspondence checking.

CITATIONS

9 sources

9 citations — click to expand

[1] C1: PIPE is a five-stage Y86-64 pipeline that adds pipeline registers to allow up to five instructions to flow simultaneously in different stages. Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[2] C2: SEQ and PIPE use similar functional blocks and stages; SEQ flow includes PC-based fetch, register reads, ALU work, data memory access, register writeback, and PC update. Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[3] C3: A modeled pipeline register can select an input value, old value for a stall, empty value for a bubble, or initial value for verification. Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[4] C4: PIPE requires additional data connections and control logic to resolve hazard conditions where data or control must pass between pipeline instructions. Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[5] C5: The STD PIPE variant uses decode-stage forwarding for execute-stage data hazards, stalls for load/use and return hazards, predicts branches as taken, and cancels up to two instructions on misprediction. Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[6] C6: PIPE variants demonstrate no-forwarding stalls, added load/use forwarding, and alternative branch-prediction policies with possible cancellation of up to two instructions. Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[7] C7: UCLID5 models the pipelined microprocessor and sequential reference implementation and supports verification scripts for Burch-Dill correspondence checking. Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[8] C8: PIPE stage modeling in UCLID5 must respect combinational signal-flow dependencies, with constraints including writeback-to-decode and memory-to-execute-to-decode. Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[9] C9: Safety-style verification alone can allow deadlocked or non-progressing processors to pass, so liveness must be verified to show that the pipeline does not stall indefinitely. Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5