Power as the Next Physics Wall for AI
Notes de l’épisode
What's common to optics and power that ruins everything in the era of AI?
Resistance.
The same physics that drove interconnects to optics is now driving low-voltage power delivery up to 800V. Austin Lyons (Chipstrat) and Vik Sekar (Vik's Newsletter) unpack it using the Kyber rack as an example.
At 600kW and 48V, you're pushing 12,500 amps through a single rack. Power loss scales with I². The math doesn't work. The fix is 800V — and the parts come straight from the EV traction inverter ecosystem (SiC, GaN, IGBTs).
We cover the full grid-to-GPU power conversion chain (substation, utility room, PSU, intermediate bus converter, VRM), why vertical power delivery is the CPO equivalent for power, and why the power industry is a much wider open problem than optics or HBM. Plus the new topology fight: 800V → 48V (reuse the existing 48V infrastructure) vs 800V → 6V (skip 48V entirely, like TI and Navitas are pushing).
We also touch Coherent's six-inch indium phosphide ramp at Järfälla, Sweden, and why margins are the real read-through next quarter.
Relevant reading:
Vik's Substack post on power: https://www.viksnewsletter.com/p/power-delivery-as-the-next-physics-wall
Google TPU 8i / 8t blog (Boardfly deep dive): https://cloud.google.com/blog/products/compute/tpu-8t-and-tpu-8i-technical-deep-dive
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Chapters
(00:00) Intro
(01:41) Memory tax: inflation, not innovation
(03:46) Boardfly: 16 hops to 7
(05:12) Coherent's six-inch indium phosphide ramp
(12:15) Power is the next physics wall
(15:08) Why 48V breaks at 600kW: 12,500 amps
(23:05) 800V and vertical power delivery: CPO for power
(30:34) Grid to GPU: every stage is a different supply chain
(39:20) 800V → 48V or skip straight to 6V?