#501 – Discussing the Open Source PDK with Tim Ansell

Released Monday, 20th July 2020
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Welcome back, Tim ‘Mithro’ Ansell!

  • Tim has been on the show twice before:

  • Tim says the next level down will be making the actual chips like Sam Zeloof, but he prefers bits to atoms.

  • Talk at Chaos with Bunnie about dabbling in the others’ fields, like thinking about the lifetime of software (and applying quality engineering)

  • What is an open source PDK? Github repo

  • Three main components to building an IC

    • The RTL and design (code)

    • The tools – compiler / interpreter in SW

    • How does the physics work?

  • Called the PDK – process design kit

  • In machine readable form

  • Similar to the stackup of a PCB

  • Tim likes the tool SKiDL by past guest Dave Vandenbout.

  • Mike Englehardt has been on before talking about SPICE.

  • Why were PDKs secret before? Especially since it would be very hard to reverse engineer the PDK

  • In the 80s it was open, but it changed over time. Chris posits because of VC investment? Now it’s cultural that the chip industry is not open

  • “Open source has won in the sofware world” and the arguments feel the same

  • QuickLogic officially supporting their tools with open source tools, as stated in a blog post by CEO Brian Faith

  • RISC V ISA (instruction set architecture)

  • “The secret power of open source means engineers don’t have to spend time talking to lawyers”

  • Open source standardizes legal equations

  • The ASIC world has many groups of lawyers

  • Only ideas that people are extremely confident about will get explored

  • Moore’s law slowing down, compute needs growing

  • Taking risks is hard because of all the roadblocks

  • RISC V has opened up the ISA space to try exploring ideas that others had written off as bad ideas

  • Tim gave a FOSSi “Dial Up” talk, which we will refer to at different timestamps to discuss the slides he reviews.

  • Single core has flattened out for 10 years (7 minute mark on the video)

  • More cores needs more memory bandwidth

  • Power consumption issues

  • Tim is in a group the focuses on developer productivity at Google

  • That’s why they’re contributing to tools to make things faster

  • Security is also dependent upon how fast you can deploy changes

  • Making hardware accelerators using TPUs

  • Using machine learning to develop TPU

  • 130 nm came out in 99 (26 minute mark)

  • The PDK and resulting silicon will be used for areas where cost > performance, like IoT.

  • Good for microcontroller, but not a high speed

  • Beagleboard has PRUs

  • They expect some users will make specialized devices, like putting a RISC V per pin or similar.

  • What’s the plan for analog?

  • First thing released was digital standard cells, but they plan to publish low level transistor models, including parametric models. Unfortunately they are currently blocked on getting that work released.

  • What tools are available?

  • Tools for doing an open source flow

  • Google will be doing a free shuttle run for open s…

  • Will be sending it to eFabless, they will bundle the shuttle

  • 40 designs total (unless they get a large response)

  • Wafer chip scale package (CSP) 4x4mm

  • 50 i/o, 40 will be for design

  • Might send back chips on castellated PCB

  • To get your design approved, it must be using the right license.

  • They will release a full list of licenses that will work, but Apache2 is guaranteed.

  • Also needs to pass DRC, which will be published in the repo soon.

  • Skywater PDK slack channel

  • Lottery system if they get more than 40 designs

  • Will be starting first run in Mid-November, Will be doing more runs after that.

  • Out of 16 mm^2, only 10 mm^2 is available. The rest will be for “the harness”, a RISC V processor that can connect ‘virtual GPIO’ to turn things on or off.

  • As a reference for size, could probably fit 10 RISC V cores on the 10 mm^2

  • In contrast to MOSIS or Europractice, they want to fab out 100 – 400 of the chips so that they can share.

  • Slack channel skywater-pdk

  • J-Core, an SH based processor

  • Power PC is now an open ISA

  • Tim has published an Inspiration document.

  • If you’re interested, you should join the mailing lists, especially the announce one.

  • The slack invite link is on the announce list. They will try to set up an invite bot for later.

  • Check out the FOSSi dial up talk series for future information about development.

  • Mohammed from eFabless will be giving a talk about Open Road and will be showcasing demo chips, which are currently out for manufacturing. These might act as good templates.

  • Need tutorials on all of the software (KLayout, MAGIC)

  • Project from University of Michigan, FASoC, treats analog design like digital design.

  • “Screaming inside their heart”

  • Craig Bishop episode

  • Adrian Tang episode

  • The physics act more ideally in the small space of silicon

  • Hoping to have a similar OSHpark for silicon

  • Chips4makers” is one that is trying to make “the OSH Park for ASICs”, but they are more focused on retrocomputing.

  • Trying to seed and build an ecosystem

  • “The things that will be most successful in this space will be those that build on each other and work together”

  • Traditional ASIC designers should be prepared to do thing differntly

  • Can open source be profitable? IBM bought Red Hat for $30B

  • The next wave of software is “software AND”, the hardware is just a means to an end

  • Contact Tim directly: tansell@google.com

  • Better to go on the slack and ask there

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