Pipeline Hazard

Concept

A pipeline hazard is a condition in a pipelined microprocessor that can prevent normal forward progress for a cycle or more, commonly requiring the pipeline to stall. In the cited Y86-64 pipeline examples, data hazards can cause decode-stage stalls, while data forwarding can resolve some load/use hazards without stalling.

First seen 5/26/2026

Last seen 5/26/2026

Evidence 3 chunks

Wiki v1

WIKI

Overview

A pipeline hazard is a condition in a pipelined microprocessor that may require the pipeline to stall rather than make normal program-execution progress in a given cycle. In the cited verification work, a pipelined processor cycle is allowed to correspond to zero steps of the sequential ISA model when the pipeline stalls to handle a hazard condition.^[1]

Pipeline hazards matter because pipelined implementations overlap multiple instructions for performance while still needing to implement the same sequential semantics specified by the instruction set architecture (ISA). Interlocking and data forwarding are used so that the overlapped execution remains faithful to the ISA model.^[2]

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RELATIONSHIPS

2 connections

Data Forwarding mentions → 100% 1e

Data forwarding is employed to handle pipeline hazards in pipelined processors.

Pipeline Stall mentions → 100% 1e

Pipeline stalls are used to handle data hazards when no forwarding path is available.

LINKED ENTITIES

4 links

Data Forwarding mitigated_by The evidence states that an added forwarding path allows some load/use hazards to be resolved by data forwarding rather than stalling.

Pipeline Stall handled_by The evidence says the pipeline stalls to deal with a hazard condition and describes decode-stage stalls caused by data hazards.

Instruction Set Architecture verification_context The evidence explains that pipelined execution must faithfully implement the sequential semantics of the ISA.

Liveness Verification requires_verification_of The evidence states that liveness must be verified to show that the processor cannot get stuck without forward progress and that the pipeline does not stall indefinitely.

CITATIONS

7 sources

7 citations — click to expand

[1] Hazard conditions can cause pipeline stalls Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[2] Pipelining overlaps instructions while preserving ISA semantics Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[3] Data hazards can stall decode for up to three cycles Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[4] Forwarding can resolve some load/use hazards Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[5] Safety checking can allow zero ISA steps during stalls Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[6] Liveness is needed to rule out indefinite stalls Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5

[7] Mispredicted branches can cancel instructions Formal Verification of Pipelined Y86-64 Microprocessors with UCLID5