Have you ever looked inside a computer and wondered how information gets stored? These days we take for granted being able to save files, photos, and videos to massive hard drives and solid state drives. But data storage had much humbler beginnings…
In this article I‘m excited to explore the history of magnetic drum memory – one of the earliest forms of storage used in computers. We‘ll look at who invented drum memory, how they worked, what role they played in early computing, and why other technologies eventually replaced them.
Understanding innovations like drum memory that paved the way can give us a new appreciation for the capabilities we have at our fingertips today. So let‘s dive in!
Overview of Magnetic Drum Memory
Magnetic drum memory refers to a data storage device used extensively in the first generations of computers in the 1940s through 60s. It provided the primary "working memory" that the computer used for internal computations and data manipulation, similar to how RAM cards temporarily hold data on today‘s machines.
The device consisted of a metal cylinder or "drum" coated on the outside with a magnetic recording material. The drum rotated at high speeds while read/write heads arranged in rings around it magnetized spots on the coating to store data or detected the magnetism to read back the stored bits.
Compared to early alternatives like delay lines using sound waves, or cathode ray tubes displaying bits as dots on a screen, magnetic drums provided a major leap forward in affordability, capacity and reliability. No wonder they became ubiquitous while playing a pivotal role in computing‘s formative years!
Now let‘s look closer at the inventor who made this breakthrough possible…
Gustav Tauschek: Creator of Magnetic Drum Memory
The credit for inventing magnetic drum memory goes to Gustav Tauschek, an Austrian engineer born April 29, 1899 in Vienna. Tauschek was a self-taught prodigy who began innovating in data storage and recording as early as 1919 when he patented an analog device to optically record speech.
In his early 20s, Tauschek began working for Rheinmetall, a German manufacturing firm, while continuing to patent new devices. His work focused primarily on advancing punched card machines which were used for accounting and data processing prior to digital computers.
During his time at Rheinmetall from 1926 to 1930, Tauschek patented:
- An electronic calculating machine (1927)
- A punch card printing device (1928)
- An optical character recognition system to read typed characters (1928)
Rheinmetall established a subsidiary firm to develop Tauschek‘s punch card innovations in 1928. But later that year the subsidiary was acquired by International Business Machines Corporation (IBM), establishing their early monopoly on tabulation equipment.
IBM retained Tauschek with a 5 year contract. During his career he would sell 169 patents to IBM, including a 1931 patent on automated letter sorting equipment using punch card encoding.
Then in 1932 Tauschek received a US patent (number 1880523) for his concept of a "magnetic drum memory device" – considered the first patent on using a magnetic surface for digital data storage.
Tauschek‘s Initial Magnetic Drum Prototypes
Tauschek‘s original magnetic drum prototype consisted of a metal cylinder coated on the outside with a magnetic recording material. His design arranged wire coils around the drum to form read/write heads occupying each track – originally just a single head per track.
The heads could be switched on and off electrically to magnetize spots on the coating as binary digits rushed by. Later heads could read back the magnetic polarities to retrieve the stored data.
Tauschek‘s patent from 1932 described a drum memory device with an estimated total capacity of 62.5 Kilobytes able to store approximately 500,000 bits along its cylindrical surface. While minuscule by modern solid state drive standards, this represented an enormous leap for a time when data capacities were measured in bits and bytes rather than gigabytes!
With roughly 200 bits available per inch of surface length, room existed for enhancement. But Tauschek made the pivotal breakthrough by showing data could be stored magnetically on a rotating cylinder and rapidly accessed again by switching read/write heads on and off.
Let‘s look at how his concept was adapted and improved upon in early computers…
Widespread Adoption as Computer Memory in the 1950s
In the 1940s and 50s, engineers recognized magnetic drums to be an ideal storage medium for early computers. They provided affordable, reasonably fast random access memory that was leaps ahead of other options of the day in capacity.
Some of the early computers to adopt magnetic drums included:
| Computer | Year | Drum Details |
|---|---|---|
| Atanasoff-Berry Computer | 1942 | 300 rpm drum storing 60 bits |
| Ferranti Mark 1 | 1951 | 8 tracks x 128 30-bit words |
| UNIVAC I | 1951 | 1,000 words of 12 chars each |
| IBM 701 | 1952 | 100,000 bits at 3,600 rpm |
| IBM 650 | 1953 | 1,000 10-digit words at 12,500 rpm |
As you can see capacity, rotation speed, and access times improved rapidly through the 50s as drums gained popularity.
In some cases like the 1956 IBM 305 RAMAC system (Random Access Method of Accounting and Control), magnetic drums were also used as early secondary storage, complementing magnetic tape drives. The RAMAC drum units spun 50 disk surfaces at 12,500 rpm providing roughly 5 MB of storage – considered the first commercial "hard drive"!
Now what eventually led to the decline of this once core computer component? Read on…
The Eventual Decline of Magnetic Drum Memory
Despite the early popularity, magnetic drum memory eventually faced growing performance limitations:
-
Seek times lagged behind hard disk drives with movable heads that could shuttle more rapidly across tracks rather than relying on drum rotation speed alone.
-
Per-bit costs were higher than magnetic tapes or flat hard drive platters with ever denser recording particles.
-
Faster, non-volatile magnetic core memory began displacing drums as primary memory in the 1950s.
-
The rise of microcomputers in the 1970s demanded compact, affordable solid state memory.
So by the 1960s magnetic core and hard disk drives started taking over applications previously dominated by drums. Their manufacture ceased entirely in the 1970s.
However drums did continue to serve a few specialized purposes well into the 1980s:
-
Digital Equipment Corporation‘s PDP-11/45 minicomputers used drums as main memory and for swap storage when running early UNIX systems.
-
The US military‘s Minuteman ICBM launch control centers relied on magnetic drum memory from the early 1960s up through a system upgrade in the mid 1990s!
So while largely obsolete, magnetic drums remained respected for roles valuing their proven reliability over latest performance – literally helping control nuclear arsenals for 30+ years!
Legacy of an Important Milestone
As we‘ve explored here, magnetic drum memory played a pivotal role in computing history by providing an affordable form of random access memory enabling new capabilities.
The concept of storing data on a magnetized spinning cylinder led directly to hard disk drive technology – which surpassed drums by using flat platters rather than cylinders, and movable read/write heads rather than fixed ones.
So next time you save a file to your multi-terabyte drive with near instant response, take a moment to appreciation innovations like the magnetic drum which pioneered the way! Devices like these established core capabilities that are simply taken for granted today.
I hope you‘ve enjoyed this dive into magnetic drum memory. Let me know if you have any other questions about this milestone data storage technology!
