CONTROL DATA <CDA> TO BUY PERIPHERALS STAKE Control Data Corp said it agreed to acquire Unisys Inc's <UIS> 13 pct stake in <Magnetic Peripherals Inc>. The letter of intent provides that Unisys converts from an owner in Magnetic Peripherals to a customer of Control Data's data storage products group over a two year period. Under the agreement, Control Data will continue to furnish disk drives to Unisys, it said. No other details of the proposed agreement were available. Magnetic Controls, managed by the data storage products group of Control Data, was founded in 1975 as a joint venture to maintain a technological base in data storage, and supply peripheral equipment for the computer systems of its owners. The venture has become a developer and manufacturer of high performance, high-capacity data storage products sold by Control Data to computer systems manafacturers worldwide, it said. After conversion of the Unisys interest, Control Data will own 80 pct, Honeywell Inc <HON>, 14 pct and Bull S.A. of France, six pct, it said.