A $725bn hyperscaler capex ramp and a 20% HBM price rise have made the South Korean chipmaker the second-most valuable company on the KOSPI. The harder question is when supply catches demand. There is a small joke in semiconductor circles about which part of an AI server is most expensive. The graphics processor used to be the obvious answer. For the past 18 months, increasingly, it has been the memory soldered next to it. On Monday, the market priced that joke. SK Hynix, the South Korean memory specialist that supplies the bulk of the world’s high-bandwidth memory for AI accelerators, climbed as much as 12 per cent in Seoul, with shares hitting roughly 1.4 million won, or about $970, in morning trading, according to Reuters. The rally made SK Hynix the second-most valuable company on the KOSPI, behind only Samsung Electronics, and reflected, the wire said, foreign buying that followed strong earnings and reaffirmed AI infrastructure plans from US hyperscalers the previous week.…