Control Data Corp is to bankroll the supplier of its Cyber line of Unix workstations, Silicon Graphics Inc, Mountain View, California, to the tune of $68.9m. It is to subscribe at $22.50 a share to a new issue of shares by the company that will give it a 20% stake in the enlarged capital. It has renewed its OEM agreement with Silicon, is considering joint development with it of supercomputer workstations, and will also get one seat on the board.