lowRISC / lowRISC/ibex

Check possibility of input silencing for critical blocks

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Component:RTL Type:Enhancement
Dominant language
SystemVerilog
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Description

@gautschimi noted in https://github.com/lowRISC/ibex/pull/746#discussion_r408876872 that in order to reduce power consumption, we should silence the inputs of large blocks or blocks with high fanout. Examples include multdiv, ALU and LSU.

Since blindly silencing all inputs of these blocks might add new muxes on the critical path, we should carefully check how to best reuse existing muxing resources.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by examining the input paths and existing muxing for the multdiv, ALU, and LSU blocks. Compare potential input silencing against added muxes on critical paths and the expected power benefit; done would be a documented recommendation or well-defined implementation plan.

Written by the indexing model from the issue text.

Assessment

Domain
embedded-iot, performance
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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