Intel rises on sale of majority stake in Altera to Silver Lake

** Shares of chipmaker Intel INTC.O up 4.1% premarket to $20.56 after announcing Altera stake sale to PE firm Silver Lake

** INTC says to sell 51% stake, valuing programmable chip unit at $8.75 bln

** Co bought Altera for nearly $17 bln in 2015, and has taken steps since last year to spin it out

** In Feb, Silver Lake was reported to be in exclusive talks to purchase a majority stake in Altera in about $9 bln deal

** Through Fri close, INTC shares have lost roughly half their value over the past one year

** Meanwhile, shares of rivals Nvidia NVDA.O and Advanced Micro Devices AMD.O rising premarket after the Trump administration granted exclusions from steep tariffs on imported semiconductor chips