CXMT shares jumped as much as 470% in its Shanghai debut, giving the memory chipmaker a ~$487B market cap, making it the most valuable China-listed company (Jenny Lee/CNBC)

Jenny Lee / CNBC: CXMT shares jumped as much as 470% in its Shanghai debut, giving the memory chipmaker a ~$487B market cap, making it the most valuable China-listed company — Shares of chipmaker Changxin Technology Group rose about 470% Monday as they debuted on Shanghai's tech-heavy STAR Market, making CXMT the most valuable China-listed company.