No. 1 ESS program store

Line and trunk translation data and operating programs for no. 1 ESS are stored in a large semipermanent memory. This memory is provided by modular units known as program stores. Each program store provides 5.8 million bits of randomly accessible permanent magnet twistor memory organized into 131,072 parallel words. The information is stored in the state of small magnets affixed to aluminum cards. Each card contains 64 forty-four-bit words. Each store is designed to operate over a duplicated common bus system for both normal and diagnostic operations. The stores have a cycle time of 5.5 μsec. Such stores are an attractive and economical solution to the problem of providing large storage capacity for information which must be protected against accidental change. To provide an efficient and routine method for updating the information content of such stores, offices are provided with card writing equipment. This includes both card handling equipment and card magnetizing equipment under system control.