antifuse bubble memory ddr sdram delay line memory drum memory dynamic random access memory eeprom eprom ferroelectric ram flash memory magnetic core memory magnetoresistive random access memory nano-ram new york non-volatile memory phase-change memory plated wire memory programmable metallization cell racetrack memory read-only memory resistive random-access memory sonos selectron tube static random access memory strategic air command twin transistor ram twistor memory united states air force video game console volatile memory volt wen tsing chow williams tube z-ram