Reiner Pope – Chip design from the bottom up
New blackboard lecture with Reiner Pope: how do chips actually work - starting with basic logic gates, and working up to why GPUs, TPUs, FPGAs, and the human brain each look the way they do.
Reiner is CEO of MatX, a new chip startup (full disclosure - I’m an angel investor). He was previously at Google, where he worked on software efficiency, compilers, and TPU architecture.
Watch this one on YouTube so you can see the chalkboard.
Sponsors
- Crusoe was one of only five GPU clouds that made the gold tier in SemiAnalysis’ most recent ClusterMAX report. Gold-tier providers like Crusoe delivered 5-15% lower TCO than silver-tier clouds, even with identical GPU pricing. This is because optimizations like early fault detection and rapid node replacement don’t necessarily show up in the sticker price, but still matter a ton in the real world. Learn more at crusoe.ai/dwarkesh
- Cursor is where I do most of my work—from reading research papers to visualizing technical concepts to coding up internal tools for the podcast. Most recently, I used it to build two different review interfaces for my essay contest, one that anonymizes submissions for scoring and another that lets me see applicants’ essays next to their resumes and websites. Whatever you’re working on, you should try doing it in Cursor. Get started at cursor.com/dwarkesh
- Jane Street let me ask Ron Minsky and Dan Pontecorvo, two senior Jane Streeters, a bunch of questions about how they use AI. We discussed everything from the types of models they’re training to how they think about the future of trading to why they’re more bullish than ever on hiring technical talent. You can watch the full conversation and learn more about their open positions at janestreet.com/dwarkesh
Timestamps
00:00:00 – Building a multiply-accumulate from logic gates
00:16:31 – Muxes and the cost of data movement
00:26:10 – How systolic arrays work
00:39:11 – Clock cycles and pipeline registers
00:51:51 – FPGAs vs ASICs
01:03:25 – Cache vs scratchpad
01:07:27 – Why CPU cores are much bigger than GPU cores
01:12:00 – Brains vs chips
01:15:33 – A GPU is just a bunch of tiny TPUs
Transcript
00:00:00 – Building a multiply-accumulate from logic gates
Dwarkesh Patel
I’m back with Reiner Pope, CEO of MatX, a new AI chip company. Last time we were talking about what happens inside a data center. Now I want to understand what happens inside an AI chip. How does a chip actually work? Full disclosure, by the way: I am an angel investor in MatX. So hopefully you have designed a good chip.
Reiner Pope
Hope so. I’ll start with the smallest fundamental unit of chip design, and we’ll build up to what an actual production chip is and what its components are. At the very bottom level of a chip, the primitives we work with are logic gates, very simple things like AND, OR, and NOT. These are connected together by wires that have to be laid out physically as metal traces on a chip.
The main function that AI chips want to compute is the multiplication of matrices. Inside that, the fundamental primitive is a multiply-accumulate of pairs of numbers. We’re going to demonstrate what that calculation looks like by hand, and then infer what a circuit would look like for that.
It’ll be easiest if I do a multi
