took far longer than the typical 30 ms to 50 ms. For example, multiply took six to nineteen revolutions of the drum (60 ms to 190 ms) and divide (an option) took ten to thirty seven revolutions of the drum (100 ms to 370 ms). Input/Output instructions could interlock the processor for as many revolutions of the drum as needed by the hardware. Hardware implementation The logic circuitry of the 305 was built of one- and two-tube pluggable units and relays. Related peripheral units A basic system was composed of the following units: IBM 305 – Processing unit, the magnetic process drum, magnetic core register and electronic logical and arithmetic circuits IBM 350 – Disk storage unit IBM 370 – Printer IBM 323 – Card punch IBM 380 – Console, the card reader and IBM Electric typewriter model B1 IBM 340 – Power supply See also List of vacuum tube computers History of hard disk drives References External links IBM 305 RAMAC Data Processing System IBM Archives on the 305 IBM 350 RAMAC site originally prepared under the supervision of the Storage Special Interest Group of the Computer History Museum Youtube video 305 Computer-related introductions in 1956