As a non-RTFA-er. I'm assuming it's a wafer-scale chip, similar to the ones made by Cerebras.
EDIT: From TechRadar[0]: "The 300mm wafer that both CEOs are holding will generate about 50 to 60 ASICs."
[0] https://www.techradar.com/pro/broadcom-and-openai-debut-jala...