NL.net proposal

2022-08-051

Project name

Libre-SOC OpenPOWER ISA RFCs

Website / wiki

https://libre-soc.org/nlnet_2022_opf_isa_wg

Please be short and to the point in your answers; focus primarily on the what and how, not so much on the why. Add longer descriptions as attachments (see below). If English isn't your first language, don't worry - our reviewers don't care about spelling errors, only about great ideas. We apologise for the inconvenience of having to submit in English. On the up side, you can be as technical as you need to be (but you don't have to). Do stay concrete. Use plain text in your reply only, if you need any HTML to make your point please include this as attachment.

Abstract: Can you explain the whole project and its expected outcome(s).

The current NLnet funding to date has allowed Libre-SOC to develop one of the most powerful Scalable Vector ISAs in the world. The 25-year-old Power ISA, developed and curated by IBM, was transferred to the OpenPOWER Foundation, and is the basis on which, with NLnet EU funding, we have based Simple-V, the Draft Scalable Vector Extension.

Simple-V needs to be submitted to the OPF ISA Working Group, for formal discussion and inclusion. Given that it is 380 pages we expect this to be done carefully and incrementally. https://ftp.libre-soc.org/simple_v_spec.pdf

However the process of submitting RFCs (Requests For Change), at the time of writing, still has not been publicly announced and opened up. We expect it to be very soon, but obviously could not begin any RFC Submission as part of earlier NLnet funding. The timing is now right.

We will become publicly informed very shortly of the procedures but anticipate it to include development and submission of Compliance Test Suites (already partly covered by Simple-V unit tests, kindly funded by NLnet) as well as ongoing work on the Simulator.

Have you been involved with projects or organisations relevant to this project before? And if so, can you tell us a bit about your contributions?

A lot! a full list is maintained here https://libre-soc.org/nlnet_proposals/ and includes

  • the world's first FOSSHW IEEE754 Formal Correctness Proofs for fadd, fsub, and fma, with support for FP Formal Proofs added to symbiyosis;
  • the world's first in-place Discrete Cosine Transform algorithm;
  • Significant improvements to Europe's only silicon-proven FOSSHW VLSI toolchain (coriolis2, by LIP6 Labs of Sorbonne University) to do an 800,000 transistor fully automated RTL2GDSII tape-out;
  • development of a 180nm Power ISA 3.0 "Test ASIC", the largest fully FOSSHW ASIC ever taped-out in Europe (and funded by Horizon 2020)
  • development of an Interoperability "Test API" for Power ISA systems, with thousands of unit tests.

and much more. The side-benefits alone for EU citizens are enormous.

Requested Amount

EUR 100,000.

Explain what the requested budget will be used for?

Time and resource, primarily manpower, to prepare and submit the documentation to OPF. To give us legal compliance for the development work carried out over the past four years, as part of the transfer to the OpenPOWER Foundation.

  • ongoing communication with the OpenPOWER Foundation ISA Working Group
  • preparation of a large number of RFCs (380 pages total so far) through the External RFC Process
  • for each RFC accepted, work needs to be done with IBM to submit Power ISA Spec changes
  • for each RFC accepted, a Compliance Test Suite must be written
  • for each Compliance Test Suite written the results must be confirmed correct by inspection (hence the Simulator) which has as we already discovered been quite a lot of work
  • Along the way we aim to continue developing the "Test API" which allows running thousands of unit tests on multiple systems and cross-checking the results. Currently we have Simulator, some "Expected Results", and the Libre-SOC HDL as well as qemu. We aim to add cavatools, gem5, Microwatt and stand-alone binary auto-generation for running on IBM POWER9 as well as Libre-SOC and Microwatt FPGAs.

Compare your own project with existing or historical efforts.

We are developing a Cray-style Scalable Vector ISA Extension for the Supercomputing-class Power ISA. Similar historic ISAs include Cray Y/MP, ETA-10, Cyber CDC 205. More recent is the NEC SX Aurora. They are all proprietary systems: Libre-SOC's efforts are entirely FOSSHW.

Open Scalable Vector ISAs include MRISC32/64 (in early development) and RISC-V RVV. Advocates of RISC-V have been discovering to their dismay that RVV and RISC-V ISA has fundamental design issues that cannot be fixed. Additionally, submission of RISCV ISA modifications requires RISCV Foundation Membership which puts us under impossible conflict of interest with Full Transparency Conditions not only with NLnet but also with EU Auditing Requirements. By direct contrast OPF External RFC Submission does not require Secrecy.

What are significant technical challenges you expect to solve during the project, if any?

The main challenge is one of communication. The majority of the technical development has been done thanks to NLnet but it was so complex and comprehensive that it risks overwhelming the ISA WG Members, whose primary driver has of course been IBM for the past 25 years.

Libre-SOC proposes taking the Power ISA into mainstream computing, including Video Decode, 3D, GPU workloads, cryptography, and Desktop and Portable devices, all of which are far different from IBM's traditional Mainframe-style multi-billion-dollar Supercomputing business. We therefore have to be both deeply respectful of their achievements, and non-disruptive to their customer base, but also appropriately assertive now that the ISA is managed by the OpenPOWER Foundation.

Describe the ecosystem of the project, and how you will engage with relevant actors and promote the outcomes?

Partly covered above, Libre-SOC is exclusively FOSSHW and full transparency is paramount. That said we recognise that no FOSSHW team is going to manufacture FOSS ASICs in 7nm (unless several billion dollars is available to buy a Foundry and open up its PDK). To that end RED Semiconductor Ltd has been formed by us as an Independent Entity, which will commercialise Libre-SOC's designs and handle any Commercially-confidential matters that a Transparency-committed FOSSHW team simply cannot. Thus, RS will join the OpenPOWER Foundation and help ensure, from the "other side of the fence", that matters progress smoothly for IBM and other OPF Members.

RED Semiconductor Ltd will the commercial point of contact for Simple-V where Organisations are unable to deal with FOSS Entities. This maximises the broad market benefit of the technology, in line with European Objectives.

We are already set to submit presentations through multiple Conferences as has been ongoing since 2019 as can be seen at https://libre-soc.org/conferences and will continue to submit press releases to OPF https://openpowerfoundation.org/blog/libre-soc-180nm-power-isa-asic-submitted-to-imec-for-fabrication/. Our entire development is public so is accessible to all.

Extra info to be submitted

the budget is high because we honestly do not know yet how much work IBM and the ISA WG expects us to do. we do however know that there will be announcements very soon. If it turns out to be less work we are more than happy to go with a proportionately smaller budget.