Why a Libre 3D CPU / GPU / VPU?

  • Study of SoCs (Allwinner, Rockchip, NXP) shows none are fully Libre
    • Either GPU driver firmware is proprietary, or VPU firmware, or bootloader
  • This causes customer product development issues
    • https://tinyurl.com/valve-steam-intel
  • Businesses are waking up to lack of transparency
    • Intel Management Engine (spying backdoor co-processor)
    • Spectre, Meltdown, CSME (Chain-of-Trust) issues
  • Solution: full transparency. All source available for everything.

How is LibreSOC being developed?

  • Using Libre (rather than "open") development practices
    • no "I'll release it when it's ready": all development is real-time public access
  • No NDAs, no hidden discussions
    • we can invite anyone (any expert) to help with review
    • free to ask for help anywhere in the world (comp.arch, stackexchange)
  • Using litex, nmigen, opencores HDL
    • heavily depending on python OO (not possible with VHDL or Verilog)
    • leap-frogging ahead by not reinventing the wheel
    • yosys converts nmigen to verilog for standard tools.

Why is it different from other SoCs?

  • LibreSOC is a hybrid CPU-VPU-GPU architecture.
    • OpenPOWER ISA itself is extended to include 3D and Video instructions
    • (SIN, ATAN2, YUV2RGB, Texture Interpolation)
    • Only after approval of OpenPOWER Foundation!
    • There is no separate GPU or VPU: it really is the same core.
    • Massively simplifies driver development and application debugging
  • Vectorisation is "Simple-V" (VSX not being implemented)
    • VSX is SIMD and is considered harmful
    • https://www.sigarch.org/simd-instructions-considered-harmful/

What is being developed? (Roadmap)

  • First simple core achieved in simulation Sep 2020
    • FPGA (ECP5) target followed shortly
  • First silicon tape-out 180nm deadline 2nd Dec 2020
    • sponsored by NLnet, with help from Chips4Makers Libre Cell Libraries
    • layout is entirely libre-licensed tools: coriolis2 from lip6.fr
  • Next chip is "SBC" style quad-core
    • similar spec to Allwinner A64, Rockchip RK3399
    • targets "Pi" boards, smartphones, tablets, Industrial IoT


  • Freenode IRC #libre-soc
  • Website https://libre-soc.org
    • mailing list, git repos, bugtracker etc.