Semiconductor stocks are posting their strongest gains since the dotcom bubble, with the Philadelphia Semiconductor Index up roughly 75% year-to-date and eyeing its best annual return since 1999. The rally has added more than $5tn in market value over two months, driven by explosive demand for AI chips and manufacturing equipment.

Big Tech's infrastructure push underpins the surge. Meta, Alphabet, Amazon and Microsoft have earmarked $725bn this year for data centers and equipment. Nvidia maintains its position as the world's largest public company at a $5.1tn market cap, but competitors are outpacing its gains. Intel shares hit dotcom-era highs after bullish CPU demand outlook, while AMD surged over 120% following supply deals with Meta and OpenAI.

Memory chipmakers Micron and SK Hynix both crossed the $1tn valuation threshold, with UBS projecting further upside potential. Equipment suppliers Lam Research and KLA have also posted significant gains amid unabated demand.

JPMorgan's Jamie Dimon cautioned that current exuberance mirrors periods before market downturns in 1972, 1986, 2000 and 2007. AllianceBernstein's Nelson Yu warned that while real demand exists, price increases could eventually trigger demand destruction as Big Tech spending may prove unsustainable.