Who invented the IBM 305 RAMAC?

IBM, founded in 1911 as the Computing-Tabulating-Recording Company, was an early leader in the computing industry. In the 1950s and 1960s, IBM produced several important mainframe computers like the IBM 701 and the IBM System/360. However, these early computers relied on sequential access storage devices like magnetic tape drives which made accessing data cumbersome. There was a growing need for a random access storage device that allowed data to be accessed directly instead of sequentially.

In the mid-1950s, IBM launched a top-secret project aimed at building the world’s first random access computer storage system. This pioneering effort resulted in the IBM 305 RAMAC, which stood for “Random Access Method of Accounting and Control.” The RAMAC project was considered vital for IBM’s future in the rapidly evolving computer industry.


[1] IBM’s Early Computers

[2] IBM Personal Computer

The Need for Random Access Memory

In the 1950s, most digital computers used magnetic drum memory for storage. Drum memory stored data in fixed blocks along tracks on a metal cylinder. To access data, the drum needed to rotate to the proper track location. This meant access was sequential – data needed to be read in the order it was stored [1].

Sequential access worked well for batch processing jobs where programs accessed data sequentially. However, emerging use cases like real-time transaction processing required the ability to quickly access data located anywhere randomly. Sequential memory was too slow for these applications [2].

Random access memory enabled data to be accessed in any order, eliminating seek time. This provided a major speed advantage compared to sequential access [3]. With random access, applications could selectively retrieve the exact data needed at any given moment, enabling real-time response.

The RAMAC Project

In 1952, IBM launched a research initiative aimed at developing a random access memory system for computers, known as the RAMAC project. The goal was to create a storage device that allowed users to quickly access stored data in any order, without needing to go through data sequentially as was required with existing magnetic tape systems.

According to the Computer History Museum, the RAMAC project was led by Rey Johnson, who assembled a team of talented engineers and researchers at IBM’s San Jose research laboratory. Some key members of the RAMAC team included Tom Gardner, Arthur Critchlow, John Lynott, and Frank Hamilton.

The project began in 1952 and ran for approximately 4 years before the final RAMAC system was completed. With the random access disk memory they developed, the RAMAC researchers succeeded in revolutionizing data storage and overcoming a major bottleneck facing the nascent computer industry at the time.

Innovations of the RAMAC System

The RAMAC system contained several groundbreaking innovations in computer memory and storage. Most notably, it was the first commercial computer system to use a magnetic hard disk drive for storage. The RAMAC’s disk drive had a storage capacity of 5 million characters (around 64KB) and enabled random access to data, which was a major improvement over sequential access tape drives (The First Disk Drive: RAMAC 350 – CHM Revolution).

The RAMAC disk used 50 aluminum disks that were 24 inches in diameter coated with magnetic iron oxide material. The disks spun at 1200 rpm and data was read by a pair of metal arms with magnetic coil read/write heads (IBM 305 RAMAC – Wikipedia). This innovative stacked disk design provided a level of storage capacity and speed not possible with other forms of memory at the time.

In addition to the disk storage system, the RAMAC 305 computer itself was an advanced vacuum tube computer that could perform up to 4,900 transactions per hour. It had an air cooling system and could quickly access any piece of data on the disk in just 600 milliseconds (RAMAC – IBM). This random data access capability allowed businesses to run inventory and payroll applications which were previously not possible on tape drive systems.

Reynold Johnson: Lead Inventor

Reynold B. Johnson (July 16, 1906 – September 15, 1998) was an American inventor and computer pioneer. A long-time employee of IBM, Johnson is said to be the lead inventor and project lead of the RAMAC computer system (Reynold B. Johnson, Wikipedia). Johnson was born in 1906 in Minnesota. He attended the University of Minnesota, achieving his BS in education administration in 1929 (Reynold Johnson, Lemelson MIT).

Johnson had an extensive career at IBM, starting in 1933. He made several key inventions in electromechanical technology before taking on the RAMAC project. Some of his pre-RAMAC inventions included a grocery scale and meat/produce pricing system as well as early hard drive technology (Reynold Johnson – Complete Biography, History, and Inventions, History Computer).

As the chief inventor behind RAMAC, Johnson assembled and led the key engineers on the project. His leadership was instrumental in designing the first commercial computer with a moving-head hard drive for data storage. Johnson continued inventing at IBM until his retirement in 1971 (Reynold B. Johnson, Wikipedia).

The RAMAC Team

While Reynold Johnson was the lead inventor behind RAMAC, its development involved several other key IBM researchers and engineers who each made important contributions to bringing the innovative system to life.

Some of the notable team members included Raymond Stern, who devised the system’s servo mechanisms and actuators, and John Haanstra, who was instrumental in designing RAMAC’s disk file memory system. Thomas Simpson spearheaded the development of the specialized read/write heads capable of storing data on IBM’s new magnetic disks.

Engineers Gardiner Tucker and John Albracht were critical in designing RAMAC’s vacuum columns and creating a workable system for swapping disk packs in and out of the drive unit. Mathematician John Backus developed algorithms and programs used by RAMAC’s processing systems. Physicist Hans Peter Luhn made vital contributions to managing the vast amounts of data stored on the magnetic disks.

Thus while Johnson was RAMAC’s driving innovator, it took a diverse team of researchers and engineers across disciplines like physics, mathematics, and mechanical engineering to make his vision of a random access disk storage system into reality.

Their combined expertise in fields like electromagnetics, servomechanisms, and information storage were all needed to create the major breakthroughs embodied in IBM’s first commercial random access memory system.

Unveiling the RAMAC

The IBM 305 RAMAC was officially unveiled on September 14, 1956 at a press conference at IBM’s 590 Madison Avenue headquarters in New York City 1. IBM highlighted the system’s groundbreaking magnetic disk storage technology, which could store over 5 million characters of data on 50 spinning aluminum disks coated in iron oxide 2. At the time, this was the highest capacity storage device ever introduced.

The announcement generated significant excitement in the computer industry and among businesses looking to modernize their data processing capabilities. The RAMAC system, along with the IBM 650, were hailed as major leaps in data storage and processing power 1. Initial customers for the RAMAC included the U.S. Navy, American Airlines, and major banks and insurance companies that needed to quickly process large volumes of records and data.

While primarily targeted at business and government applications, IBM also promoted the RAMAC for scientific uses like weather prediction and atomic energy calculations 1. Over 1,000 RAMAC systems were eventually installed across the world, cementing its status as the first commercially successful computer with a hard disk drive and random access memory.

Legacy and Impact

The IBM 305 RAMAC system paved the way for major advancements in computer memory and storage technology. As the first commercial computer with a hard disk drive, RAMAC introduced the idea of random access storage and large capacity memory to the computing world (The First Disk Drive: RAMAC 350 – CHM Revolution). This allowed data to be accessed randomly instead of sequentially, enabling powerful new capabilities like databases and business computing applications.

RAMAC disks could store over 5 million characters of data, a massive leap over previous magnetic tape storage systems which held just a few thousand characters. This expanded capacity meant businesses and government agencies could store large databases, inventories, and other mission-critical information directly on a computing system for the first time (The Impact of the IBM RAMAC 35). RAMAC systems were adopted by US government agencies like the US Air Force and pioneered commercial uses like banking transactions and airline reservations.

While RAMAC’s 50 spinning platters may seem primitive today, the underlying concept inspired generations of disk drives with ever greater capacity through technological enhancements like smaller disk sizes, stacking platters, and magnetic or laser read/write heads. RAMAC laid the groundwork for modern solid state and cloud storage, while also influencing the development of large-scale business data processing.

Later Careers of the Inventors

After the RAMAC project, the team members went on to have illustrious careers at IBM and beyond. Reynold Johnson, the lead inventor, continued working at IBM as director of development and later as vice president of development programs. Under his leadership, IBM developed the first hard disk drive for commercial use, the IBM 350 disk storage unit. Johnson received the National Medal of Science in 1985 for his contributions to computer memory systems.

Other RAMAC team members also had impressive careers. James Birkenstock went on to manage the development of the IBM 1311 disk storage drive. William Goddard became an IBM vice president and oversaw the team that developed the IBM System/360. Frank Hamilton managed the Advanced Systems Development Division, working on innovations like bubble memory. The RAMAC project was just the beginning for this talented group of engineers and inventors.


The IBM 305 RAMAC system marked a major milestone in the history of computing. As the first commercial computer to utilize a moving-head hard disk drive for large-scale random access memory storage, it pioneered technology that would become universal in later computers. The RAMAC’s capacity of 5 million characters was unprecedented for the 1950s and allowed new applications with fast access to large databases.

Beyond its technical achievements, the RAMAC highlights the importance of innovation in the early days of computing. Its development required not only engineering brilliance but also business acumen and risk-taking by Thomas Watson Jr. and IBM. The RAMAC project was an ambitious endeavor involving close collaboration between various teams working on an untested concept. Their success paved the way for later advances.

Over six decades after its debut, the RAMAC’s novel use of spinning disks remains the fundamental design of hard drives today. It was an important step in computing history, demonstrating the possibilities of memory storage and processing power beyond what was imaginable at the time.