Reiner Pope – Chip design from the bottom up
5/22/20261 hr 21 min
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. Read the transcript.
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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
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Clips
Transcript preview
First 90 secondsDwarkesh Patel· Host0:00
I'm back with Reinier Pope, who is the CEO of Madix, which is a new AI chip company. Last time we were talking about what happens inside a data center. Now I wanna understand what happens inside an AI chip. How does a chip actually work? Full disclosure, by the way, I am an angel investor in Madix. Um, so hopefully you have designed a good chip [laughs]. [laughs] Also, if you're listening to this on an audio platform, it's much preferable to watch this blackboard lecture on a platform where you can see what's happening. So switch over to YouTube or Spotify.
Reiner Pope· Guest0:31
So I'll start with, uh, sort of the very smallest fundamental unit of, of, of chip design, then we'll sort of build up into what an overall, um, like, actual production chip, uh, what are the components of that.
Dwarkesh Patel· Host0:41
Yep.
Reiner Pope· Guest0:41
At the very bottom level of a chip, the primitives that we work with are, uh, logic gates, um, which are very simple things like and, or, not. Um, and then these are connected together by, by wires that have to be laid out, uh, physically as metal traces on a chip. The main function that, that AI chips want to, uh, compute is, uh, multiplication of matrices, and really inside that is the fundamental primitive is multiply-accumulate of just, like, of, of pairs of numbers. So we're gonna sort of demonstrate what that calculation looks like by hand, and then sort of infer what, what a, uh, circuit would look like for that. It'll turn out to be sort of easiest if, if I do multiplication, uh, accumulate of something like a, um, a four-bit number, um, w- with another four-bit number. Um, and then