Building a Chip Design Team for Raspberry Pi

Welcome back James Adams and Liam Fraser

• The RP1 is the new custom silicon on the Raspberry Pi 5 that is the helper chip to the Broadcom part onboard
• The HW team was last on the show in 2021 talking about the RP2040
• They have been working on the RP1 since 2015
• It’s a small team, especially compared to other companies doing custom silicon.
• RP2040 update
• Scripting to reconfigure the silicon clocks/blocks
• Are they making other chips?
• Divvy-ing up duties for silicon
• Broadcom is making the processor and took input for this latest
• Dialog/Renesas do the power chip on the RPi5
• PIO
• Chris gave an example of a board (the Ostentus) where the PIO is just listening for i2c messages and passing them up the stack.
• Design goal was to do cycle by cycle processing
• Someone on twitter having PIO talking to fiber transceivers
• Sourcing and RP2040 availability
• They get 20000 chips per wafer
• Buying wafers a few at a time through IMEC, sometimes through TSMC directly
• There are often small amounts of availability of “wafer starts”
• TSMC40
• IP block updates: USB 3 / Ethernet
• Can do diffs on the verilog
• Receiving high paid IP
• Liam is the sysadmin / servers are on site
• Buying from Synopsis
• Stitching together IP
• They list what version of the IP they’re using in the various sections of the datasheet.
• Prototyping on FPGAs
• Controller and Phy interface are exposed
• ProFPGA system with daughtercards
• Can’t run at full clock speed on FPGA
• Digital vs analog simulation
• Could someone (competitors) copy things?
• As open as possible, being open where it provides value
• Cost savings on the RP2040
• Traditionally the “Southbridge” is the IO hub for computing, the Northbridge was the cache/memory (later subsumed into large CPUs)
• 2712 on RPi is 16 nm
• This model of creating different generations of silicon but putting them all together is similar to chiplets but…on a PCB
• There is a (hidden-ish) PIO in the RP1.
• There will be more processing delays in RPI5 to deal with, but they won’t be noticable because Linux is already pretty not-real-time
• Hoovering up more functions in one chip
• Layout of connectors changed again
• Pins are created to be well laid out on the PCB
• RISC V foundation
• The stack / ecosystem isnt as mature
• James’ signature is under the USB3 connector
• RPi5 is “the most raspberry pi raspberry pi” yet