Role in inference
Jalapeño is inference-only. It does not target training, which OpenAI continues to run on purchased GPU capacity. The rationale is straightforward arithmetic: a model is trained a finite number of times but served continuously, so at OpenAI's traffic volumes even a modest improvement in cost per token compounds into a very large number.
What makes the design interesting is that OpenAI had information no merchant vendor has — precise knowledge of how its own models behave in production, which operations dominate, where data movement is wasteful, and what the real balance between compute and memory should be. The company has described designing the architecture around those observed bottlenecks rather than around a general notion of what an AI accelerator should do. That is the strongest available argument for captive silicon, and it is unavailable to anyone selling into a broad market.
The choice of HBM over cheaper memory is the most revealing decision. Many inference ASICs economise on memory to reach a lower price point. OpenAI, serving latency-sensitive interactive products at enormous scale, evidently concluded that memory bandwidth was not the place to save money.