The Other Half of Compute

The Other Half of Compute xAI stood up its first 100,000 GPUs in Memphis in 122 days. It doubled that in another 92. By early 2026 the site, Colossus, held around 555,000 of them, building toward two gigawatts of power, for a reported 18 billion dollars. 1 Two sophisticated people can look at that number and reach opposite conclusions. Jensen Huang’s view is that the only real risk is underspending. He puts the buildout at a trillion dollars and counting, and argues the company that holds back capacity loses the decade. 2 Dario Amodei and Ray Dalio sit on the other side. Amodei has said it can be rational not to buy unlimited compute, because the revenue to justify it may arrive on a timeline that bankrupts whoever guessed wrong. Dalio keeps making a narrower point: a technology can succeed completely and still ruin the people who financed it. 3 Same buildout. Same dollar figure. One camp calls it the obvious move of the decade and the other calls it the setup for a wipeout. They are not disagreeing about the facts. They are reading the same number and the number is the problem. What 18 billion dollars buys Every token a model produces runs down a physical path. Electricity has to be generated, moved across a grid, and stepped down through transformers to a voltage a data centre can use. Chips have to be fabricated at advanced nodes, which in practice means TSMC and a single supplier of the lithography machines that make the process possible. The chips have to be wired together with optical interconnect, assembled into racks, and kept cold. None of those layers move at the same speed, and the slowest one always sets the schedule. For four years the slowest layer kept changing. In 2022 the constraint was GPUs themselves. In 2023 it was the high-bandwidth memory stacked next to them. In 2024 it was the advanced packaging that bonds the two together. By 2025 it was photonics, the lasers and transceivers that move data between racks. By 2026 it had reached power and the