The move comes at a time puzzling to market analysts, as Mentor Graphic's stock is rising.
Last year, perhaps, Mentor might have seemed a likely candidate for Icahn's style of activism. Its stock was coming off a record low. Revenue was down and Mentor was running in the red amid a historic decline in the technology industry.
Since then, however, Mentor stock has more than doubled to $9.12, buoyed by its core market, the computer chip industry.
With its market share climbing, Mentor forecasts it will return to profitability this year and revenue near an all-time high. Shareholders just re-elected Mentor's board of directors, so it's an especially hard time to force a change.
Read more at OregonLive.com.