p.xobs.io/fa23

The State of Open Silicon

Sean "xobs" Cross, Foosn PTE Ltd

About Me

Open Silicon

Talk Outline

  1. What does it mean for silicon to be "open"?
  2. What can we do today?
  3. What can't we do today?
  4. Where can we go from here?

What does it mean for silicon to be "open"?

Availability of:
  1. Manuals
  2. Source
  3. Tooling
  4. GDSII

Parts of chip design

  1. Nondisclosure Agreements
  2. Process Design Kit (PDK)
  3. EDA Software (tooling)
  4. IP (libraries)

Nondisclosure Agreements

NDAs are required for using many packages

Process Design Kit

Example PDK stackup

EDA Software

  • Synthesis
  • Power generation
  • Clock tree synthesis
  • Place and route
  • Verification
  • Simulation

Industry tools cost $1mm plus per seat

IP Blocks

  • PCIe Controllers
  • Radios
  • Standard cells

Digital design (In The Beginning)

Motorola 6502, image © 2016 Pauli Rautakorpi

GD32F103CBT6

Image © 2016 Zeptobars

Digital Synthesis (Today)


						module and_four(input A, input B,
													  input C, input D,
													  output X);
							assign X = A & B & C & D;
						endmodule

Where are we now (in open source)?

Things are looking pretty good!

Nondisclosure Agreements

Open PDKs

  • Real PDKs
    • SKY130
    • GF180MCU
    • SG13G2
  • "Fake" PDKs
    • FreePDK45
    • ASAP5
    • Many more!

Hardware Synthesis

  • Yosys (Verilog)
  • Plugins:
    • GHDL (VHDL)
    • UHDM (SystemVerilog)

Placement, Routing, PDN, etc...

Direct Cell Design and Inspection

Available IP

    • CPU
    • FPGA
    • SPI
    • USB
    • AES
    • DAC
    • ADC
    • PLL

Standard cells

  • SKY130
  • GF180MCU
  • OSU018
  • LibreSilicon

What can't we do today?

Memories are still hard

  • Density is constantly improving
  • Expect kilobytes of RAM on a chip
    • Compare to megabytes of cache
  • A ~4x increase is possible
  • Experimental ROM support
RAM, Registers, CPU
RAM, Registers, CPU
RAM, Registers, CPU
16 kB RAM, 3.3V

Nonvolatile storage is still hard

  • No EEPROM or flash
  • ReRAM is experimental on SKY130
  • Just use external SPI flash

PDKs are large nodes

Flicker LED circuit, 3µm, image © 2015 Zeptobars

Analogue IP is still difficult

  • Some tapeouts exist, but documentation is scarce
  • Need more integration examples

What about taping out chips?

  • Google OpenMPW
  • ChipIgnite
  • EuroPractice
  • Muse
  • SIMC
Expect to pay $10,000 - $50,000

Where are we going from here?

And how you help

More open projects

developers.google.com/silicon

Education

$25 tinytapeout.com

Zero-to-ASIC zerotoasiccourse.com

More analogue design

app.siliwiz.com

Smaller process nodes?

  • OpenROAD has been tested on smaller nodes
  • No deep-submicron NDA-free PDKs yet

More involvement

  • OpenMPW -- developers.google.com/silicon
  • Tiny Tapeout -- tinytapeout.com
  • Siliwiz -- app.siliwiz.com

Thank you

Questions?