Tandem Computers' earnings rose 66% to $105.6 million for the fiscal year ended Sept. 30. Revenue for the year was up 35% to $1.035 billion, a record for the Cupertino, Calif.-based computer manufacturer. For the fourth quarter, income increased 41% to $30.4 million, compared to a year ago. Quarterly revenue was up 32% to $291 million, compared to the 1986 quarter. The company attributed the gains to healthy international business and strengthening domestic demand.