Drum memory of a Polish ZAM-41 computer

Drum memory is a data storage device and was an early form of computer memory that was widely used in the 1950s and into the 1960s, invented by Gustav Tauschek in 1932 in Austria. DDR SDRAM ( double data rate synchronous dynamic random access memory) is a class of memory Integrated circuit used in Computers It achieves nearly twice Static random access memory (SRAM is a type of Semiconductor memory where the word static indicates that unlike ''dynamic'' RAM (DRAM, it does not Z-RAM, short for " zero capacitor RAM " is a new type of Computer memory in development by Innovative Silicon Inc Twin Transistor RAM ( TTRAM) is a new type of Computer memory in development by Renesas The Williams tube or the Williams-Kilburn tube (after inventors Freddie Williams and Tom Kilburn) developed about 1946 or 1947 Genesis in radar The basic concept of the delay line originated with World War II Radar research as a system to reduce clutter from reflections from the ground Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, is Computer memory that can retain the stored information A programmable read-only memory ( PROM) or field programmable read-only memory ( FPROM) is a form of digital memory where the setting of each bit is EEPROM (also written E2PROM and pronounced e-e-prom or simply e-squared which stands for E lectrically E rasable P rogrammable An EPROM, or E rasable P rogrammable '''''R'''ead-'''O'''nly '''M'''emory'', is a type of memory chip that retains its EEPROM (also written E2PROM and pronounced e-e-prom or simply e-squared which stands for E lectrically E rasable P rogrammable Flash memory is non-volatile computer memory that can be electrically erased and reprogrammed Ferroelectric RAM ( FeRAM or FRAM) is a Random access memory similar in construction to DRAM but uses a Ferroelectric layer instead Magnetoresistive Random Access Memory ( MRAM) is a non-volatile computer memory ( NVRAM) technology which has been under development since The programmable metallization cell, or PMC, is a new form of non-volatile Computer memory being developed at Arizona State University and Phase-change memory (also known as PCM, PRAM, PCRAM, Ovonic Unified Memory, Chalcogenide RAM and C-RAM) is a type This article is about the music device manufacturer For the computer memory system see SONOS. Resistive random-access memory ( RRAM) is a new Non-volatile memory type being developed by Fujitsu, Sharp, Samsung, Micron IBM Racetrack Memory is an experimental Non-volatile memory device under development at IBM 's Almaden Research Center by a team led by Stuart Nano-RAM is a proprietary Computer memory technology from the company Nantero. Magnetic core memory, or ferrite-core memory, is an early form of Random access Computer memory. Prehistory twistor memory Bubble memory is largely the brainchild of a single person Andrew Bobeck. Twistor is a form of Computer memory, similar to Core memory, formed by wrapping or closing Magnetic tape around a current-carrying wire A data storage device is a device for recording (storing information (data The 1950s Decade refers to the years of 1950 to 1959 inclusive The 1960s decade refers to the years from the beginning of 1960 to the end of 1969 Year 1932 ( MCMXXXII) was a Leap year starting on Friday of the Gregorian calendar. Austria (Österreich ( officially the Republic of Austria (Republik Österreich For many machines, a drum formed the main working memory of the machine, with data and programs being loaded on to or off the drum using media such as paper tape or punch cards. Punched tape or paper tape is a largely obsolete form of Data storage, consisting of a long strip of paper in which holes are punched to store data Drums were so commonly used for the main working memory that the machines were often referred to as drum machines. Drums were later replaced as the main working memory by core memory, which was faster and had no moving parts, and which lasted until semiconductor memory entered the scene. Magnetic core memory, or ferrite-core memory, is an early form of Random access Computer memory. A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that

A drum is a large metal cylinder that is coated on the outside surface with a ferromagnetic recording material. Ferromagnetism is the basic mechanism by which certain materials (such as Iron) form Permanent magnets and/or exhibit strong interactions with Magnets it It is, simply put, a hard disk platter in the form of a drum rather than a flat disk. A hard disk platter (or disk is a component of a Hard disk drive: it is the circular disk on which the magnetic data are stored A row of read-write heads runs along the long axis of the drum, one for each track. Disk read/write heads are mechanisms that read Data from or write data to Disk drives The heads have gone through a number of changes over the years

The drums of the Atanasoff–Berry Computer stored information using regenerative capacitor memory. The Atanasoff–Berry Computer ( ABC) was the first electronic Digital Computing device Regenerative capacitor memory is a type of computer memory that uses the electrical property of Capacitance to store the Bits of data

A key difference between a drum and a modern disk is that on a drum, the heads do not have to move, or seek, in order to find the track they are looking for. Seek time is one of the three delays associated with reading or writing Data on a Computer 's Disk drive, and somewhat similar for CD or This means that the time to read (or write) any particular piece of data is shorter than it would be on a disk; the controller simply waits for the data to appear under the proper head as the drum turns. The performance of the drum or of a fixed head disk is defined almost entirely by the rotational speed, whereas in a moving head disk, both rotational speed and head movement rates are important.

Performance was still an issue, however. So, when a drum was used as the main working memory of the machine, programmers often took to hand-writing the code onto the drum in a particular fashion in order to reduce the amount of time needed to find the next instruction. They did this by carefully timing how long it would take for a particular instruction to run and the computer to ready itself to read the next instruction, then placing that instruction on the drum so that it was just arriving under the heads at that point in time. This method of timing compensation is called the Skip Factor or interleave, and was used for many years in hard disk controllers. Interleaving in Computer science is a way to arrange Data in a non- Contiguous way in order to increase performance

In the modern day, in BSD Unix and its descendants, /dev/drum is the name of the default swap device, alluding to the use of drum secondary-storage devices as backing store for pages in virtual memory. Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer Virtual memory is a Computer system technique which gives an application program the impression that it has contiguous working memory while in fact it may be physically

External links

• The Story of Mel – the classic story about one programmer's drum machine hand-coding antics
• Librascope LGP-30 – The drum memory computer referenced in the above story, also referenced on Librascope LGP-30. LGP-30, standing for Librascope General Purpose and then Librascope General Precision, was an early "off the shelf" computer manufactured by the Librascope
• Librascope RPC-4000 – Another drum memory computer referenced in the above story