2025-01-27 Ordinary Meeting Notes

Date

Jan 27, 2025

Disclosures

RISC-V Disclosure Video

Open

Participants

Agenda

• Meeting schedule

• Membership status

• Confluence migration

• Extension Logic Interface Workshop

Meeting schedule

• Poll results

  • Respondents favor Friday morning

• Next meeting

  • 14 February, 7 am (Pacific Time)

• Biweekly, half hour

Membership status

• Update Participation and Voting Rights by 6 February

Confluence migration

• All active documents from administrative github repository (riscv-admin) have been migrated to Confluence (charter, requirements, etc.)

• Agendas, slides, and minutes from prior meetings remain in github repository

• Future meetings will use Confluence

Extension Logic Interface Workshop

• 31 January, 7:00 am - 10:00 am Pacific Time

• Online, RISC-V members only

• Agenda

  • 7:00: RV disclosures

  • 7:05: Jerry Zhao, ROCC (20 mins + 5 mins Q&A)

  • 7:30: Christian Herber, CV-X-IF (")

  • 7:55: Andreas Koch, SCAIE-V (")

  • 8:20: Jan Gray, CXU-LI (")

  • 8:45: Open discussion and synthesis (up to 75 mins)

  • 10:00: End

• Some possible open discussion topics

  • How do these interfaces compare and contrast?

    • Extension state models

    • What hart state may be read/writeable by custom instructions – regs, CSRs, memory, control flow, exceptions, …?

    • Pipeline issues incl. singaling (comb, fixed, var latency), dependence tracking, speculation, memory ordering?

    • System topologies?

    • Reuse and verification ecosystem

  • Support for composition of custom extensions?

  • Support for arbitrary, or fixed, custom instruction encodings?

  • Support for optional "pay as you go" capabilities?

  • Value of "modular composability" (stable CPU / XU RTL)?

  • Might you bridge one interface to another?

Notes & Action Items