Universität Klagenfurt Ed. . Magnetic Drum

Drum memory was a magnetic data storage device invented by Gustav Tauschek in 1932 in Austria. Drums have been broadly used in the 1950s and into the 1960s as laptop memory. Many early computer systems, called drum computers or drum machines, used drum memory as the principle working memory of the pc. Some drums have been additionally used as secondary storage as for example varied IBM drum storage drives and the UNIVAC FASTRAND sequence of drums. Drums had been displaced as primary pc memory by magnetic core Memory Wave Workshop, which offered a better balance of measurement, velocity, price, reliability and potential for further improvements. Drums had been then replaced by exhausting disk drives for secondary storage, which have been both inexpensive and offered denser storage. A drum memory or drum storage unit contained a large metal cylinder, coated on the skin floor with a ferromagnetic recording materials. It might be considered the precursor to the arduous disk drive (HDD), however within the type of a drum (cylinder) quite than a flat disk.



In most designs, a number of rows of mounted learn-write heads ran along the long axis of the drum, one for each observe. The drum's controller merely selected the right head and waited for the data to appear under it because the drum turned (rotational latency). Not all drum items have been designed with every monitor having its own head. Some, Memory Wave Workshop such as the English Electric DEUCE drum and the UNIVAC FASTRAND had multiple heads moving a short distance on the drum in distinction to trendy HDDs, which have one head per platter surface. In November 1953 Glenn E. Hagen of Logistics Research, Inc. revealed a paper disclosing "air floating" of magnetic heads in an experimental sheet metal drum. Flying heads became customary in drums and laborious disk drives. Magnetic drum models used as primary memory were addressed by word. Drum items used as secondary storage were addressed by block. A number of modes of block addressing had been attainable, relying on the gadget.



Blocks took up an entire observe and Memory Wave had been addressed by observe. Tracks were divided into mounted length sectors and addressing was by track and sectors. Blocks have been variable size, and blocks had been addressed by track and report quantity. Blocks have been variable size with a key, and might be searched by key content material. Some units were divided into logical cylinders, and addressing by track was actually logical cylinder and observe. The performance of a drum with one head per observe is comparable to that of a disk with one head per observe and is decided almost fully by the rotational latency, whereas in an HDD with shifting heads its performance includes a rotational latency delay plus the time to place the pinnacle over the specified track (search time). In the era when drums have been used as fundamental working memory, programmers typically did optimum programming-the programmer-or the assembler, for example IBM’s Symbolic Optimum Assembly Program (Cleaning soap)-positioned instructions on the drum in such a way as to scale back the period of time wanted for the next instruction to rotate into place below the top.



They did this by timing how long it might take after loading an instruction for the computer to be ready to read the following one, then putting that instruction on the drum so that it might arrive underneath a head simply in time. This method of timing-compensation, known as the "skip factor" or "interleaving", was used for many years in storage memory controllers. Tauschek's unique drum memory (1932) had a capability of about 500,000 bits (62.5 kilobytes). One of many earliest functioning computers to make use of drum memory was the Atanasoff-Berry laptop (1942). It saved 3,000 bits; however, it employed capacitance rather than magnetism to store the data. The outer floor of the drum was lined with electrical contacts leading to capacitors contained within. Magnetic drums have been developed for the U.S. Harvard University, IBM and the University of Manchester. An Period drum was the internal Memory Wave for the ATLAS-I pc delivered to the U.S.