Magnetic Drum Memory Explained – Everything You Need To Know

Magnetic drum memory was a magnetic data storage device. Since its founding in 1932, the drum became the backbone of many early computers. It formed the primary working memory of the computer and sometimes served as the secondary storage.

But later on, the magnetic core memory and hard disk drives came into existence and replaced the drums. That’s because they offered better size balance, reliability, and high speed, and had the potential for further enhancements. Besides, they had a denser storage capacity than drums. Due to that, the manufacturing of drums stopped in the 1970s.

6 Facts about the Magnetic Drum Memory

• Magnetic drum memory was the first magnetic data storage device and an early computer memory form to be created.
• Gustav Tauschek is the mind behind the famous magnetic drum memory.
• The drum memory was the first magnetic data storage device for computers.
• Magnetic drum memory had a capacity of about 62.5 KB.
• The data storage device could store 500,000 bits across its total surface
• The principles at work in magnetic drum memory helped to lead researchers to create another and even more important innovation: the hard disk drive.

Magnetic Drum Memory History 

Magnetic drum memory was the first magnetic data storage device and an early computer memory form to be created. The data storage memory was designed and developed by the Austrian engineer GustavTauschek in 1932 in Austria. 

The device played a vital role in computer memory development and was initially used in Atanasoff-Berry computers (ABC computer) in 1942. However, most people and computer users adopted its use between 1950 and 1960.

Gustav Tauschek, born on April 29, 1899, was an exceptional self-taught Viennese engineer who also invented many other devices and systems for punch card machinery. He is also the mind behind the first OCR (Optical Character Recognition) machine, better known as the reading machine, invented in 1928.

While working for Rheinmetall in Sömmerda, Germany, between 1926 and 1930, Tauschek created a complete accounting system based on punched cards. However, the accounting system was never mass-produced. 

In the spring of 1928, Rheinmetall came up with a subsidiary company for developing new punch card-based machines. But towards the end of the same year, IBM bought the subsidiary, assuming its monopoly on the market. In the process, Tauschek received a five-year contract and sold to IBM about 169 patents in his lifetime.

In 1932, Tauschek obtained a US patent for his magnetic drum device (see US patent 1880523 and the lower patent drawing).

In its basic form, the magnetic drum memory had a metal cylinder coated with a ferromagnetic recording material.

Many considered it a precursor to the hard disk drive (HDD) but in the drum form rather than a flat disk. Most designs featured one or more rows with fixed read-write heads, designed along the drum’s long axis and each one occupying a track.

The drum’s controller task was to select the right head and then wait for the appearance of data beneath it as the drum rotated. At the same time, stationary write heads emitted an electrical pulse to alter the magnetic orientation of a particle at a specific position on the drum.

On the other hand, the read heads, also stationary, recognized a particle’s orientation as binary 1 or 0. Tauschek’s prototype could store 500,000 bits across the drum’s total surface. It had a capacity of about 62.5 KB.

Magnetic Drums Used into the 1980s

As late as 1980, the magnetic drums were still used as the main memory by many people with the PDP-11/45 machines. Drums for swapping were also still in use at various original UNIX sites.

Besides, the minuteman ICBM launch control centers continued to use the magnetic drum memory units after adopting them in the early 1960s. They only changed after the REACT upgrades that occurred in the mid-1990s.

In the modern-day, the BSD Unix and its descendants are the name of the default swap device. It originates from the use of the drum secondary storage devices as backup storage for pages in virtual memory.

By following the principles at work in magnetic drum memory, researchers have created another more advanced innovation named the hard disk drive. However, there are slight differences between the magnetic drum memory and the modern hard disk drive. 

For instance, the magnetic drum heads did not have to move to the track access, and the controller waited for the data to appear beneath the relevant head as the drum turned. With the modern disk drive, the disk head takes a particular time to move into its place. Also, the performance of a drum with fixed heads is entirely determined by its rational speed.

Magnetic Drum Memory: How It Worked

Magnetic drum memory consisted of a metal cylinder or drum coated with a ferromagnetic recording material. In between the drum, there were rows fitted with fixed read-write heads arranged along the drum’s axis, occupying each track. 

The memory device also had a controller whose major work was to select the proper head and wait for data to appear beneath it as the drum rotated.

On the other hand, the stationary write-heads emitted an electrical pulse, changing the magnetic orientation of a particle at a specific position on the drum. The process generated a series of binary digits. The read heads, which were also stationary, recognized a particle’s orientation as either a binary 1 or 0.

Magnetic Drum Memory: Historical Significance

Through the invention of the magnetic drum memory, many developers dwelled on its principles and designed various modern random access memory cards and secondary storage devices, better known as hard disk drives for their computers.

The modern hard disk drives also have magnetic storage systems with more premium features. With the many advancements, computer manufacturers have streamlined their services to produce computer devices able to accommodate the current hard drive disks.