Shares of Micron Technology Inc. MU, +4.79% jumped 3.5% toward a 20-year high in premarket trading Tuesday, after the memory chip maker raised its financial guidance for the fiscal first quarter. The updated guidance comes ahead of the further updates Chief Executive Sanjay Mehrotra is expected to share at the Credit Suisse Annual Technology Conference. Micron raised its guidance range for adjusted earnings per share for the quarter to Dec. 3 to 69 cents to 73 cents from 40 cents to 54 cents, for revenue to $5.70 billion to $5.75 billion from $5.0 billion to $5.4 billion and for reported gross margin to 28.5% to 29.5% from 25.5% to 27.5%. The stock, which is on track to open at the highest price seen during regular-session hours since September 2000, has run up 40.1% over the past three months through Monday, while the PHLX Semiconductor Index SOX, +1.69% has climbed 15.6% and the S&P 500 SPX, +1.42% has tacked on 2.7%.