History of Computer Memory
Random Access Memory

Basics of RAM

Let's start with the basic terminology of the types of RAM memory that most of us are familiar with:

• RAM - Random Access Memory - This type of computer memory can be accessed randomly. It is made up of integrated circuits that allow data to be accessed in any order (random). Any bite of memory can be accessed without touching the preceding bytes. A good definition found at Wikipedia (2010) - "Random refers to the idea that any piece of data can be returned in constant time regardless of its physical location and whether it is related to the previous piece of data." This is one of crucial aspects of why this type of memory is used today and how computers become more efficient, smaller and cheaper.

There are two types of RAM:

• DRAM - Dynamic Random Access Memory - This type of RAM stores a bit of data in a separate capacitor within an integrated circuit. This type of RAM has to be refreshed periodically. This type of memory is volatile (data is lost when not powered). This is the main type of memory found in most computers today.

• SRAM - Static Random Access Memory - This type of memory is faster and more reliable than DRAM. It does not need to be refreshed like DRAM. This type of memory is volatile, meaning bits of data are lost when the memory is not powered. SRAM is mostly used as memory cache due to the fact it is much faster than DRAM.

RAM Photos:                                                                                

A good definition for you to remember, "Computer memory refers to the physical devices used to store data or programs (sequence of instructions) on a temporary or permanent basis for use in an electronic digital computer. Computers represent information in binary code, written as sequences of 0s and 1s. Each binary digit (or "bit") may be stored by any physical system that can be in either of two stable states, to represent 0 and 1. Such a system is called bistable." (Wikipedia, 2008).

Ready to test yourself?

A Brief History of the Evolution of RAM Computer Memory

Let's focus on the major types of computer memory in history.

• Vacuum Tubes - A vacuum tube or thermionic valve could be used to create an electrical signal by controlling electrons movements in a vacuum of space. The Geissler Tube was developed by Heinrich Geissler in 1857. The Crookes Tube was developed by William Crookes. Many scientist in the 19th century experimented with vacuum tubes, Eugen Goldstein, Nikola Tesla and Thomas Edison. In the 1940's research was conducted on cathode ray tubes as data storage. In 1946 Sir Fredrick Williams and Tom Kilburn co invent the Williams Tube , a type of cathode ray tube. In 1948 Kilburn designed the Manchester Baby- the first computer to use a stored program. Vacuum tubes were connected to relay lines made up of mercury and nickel wire (precursor to core memory). In 1946 the Eniac computer was built. " The ENIAC contained 17,468 vacuum tubes , along with 70,000 resistors, 10,000 capacitors, 1,500 relays, 6,000 manual switches and 5 million soldered joints. It covered 1800 square feet (167 square meters) of floor space, weighed 30 tons, and consumed 160 kilowatts of electrical power." (Inventors.about.com, 2010)

Photo - Early Vacuum Tube 1940- 1950:           1950-1960  

• Drum Memory - Invented in 1932 by Gustav Tauschek, used throughout the 1950's and 1960's, drum memory used a metal cylinder coated with ferro-magnetic material. The drums have read and write heads along the axis. Media such as paper tape or punch cards were used to feed instructions onto the drum. This was an early form of (read only memory). The heads were fixed so seek time is determined by rotational speed. The electronic drum memory - 1942, was a magnetic storage device which was eventually replaced by core memory.

Photo- Early Drum Memory 1932                                 1950's IBM 650              

Magnetic Drum memory video:   http://www.youtube.com/watch?v=eIpoA7Ir9p8

• Core Memory - Uses magnetic ferrite rings which have wires threaded thru them. Information can be stored by the polarity of the magnetic field they contain. "Sending current through the wires causes the core to hold a charge to represent zero or one." (White, 2008). The first magnetic core patent was issued to Fredrick Viehe in 1947. Core memory was further developed by Ann Wang. Kenneth Olsen also developed magnetic core memory in 1947. Most notably he improved upon (Jay Forrester -1949 core memory) original system. Olsen co founded Digital Equipment Corporation. Forrester invented random -access, coincident-current magnetic storage.

                                    Photo - Jay Forrester 1951 files patent for Core Memory                  

• Transistor/ Semiconductors - "A transistor is essentially a vacuum tube built not to human size but on a microscopic scale. Because it's small, a transistor requires less power to generate the flow of electrons. Because it uses less power, a transistor generates less heat, making computers more dependable." (White, 2008)   "Transistors are not used simply to record and manipulate numbers.   The bits can just as easily stand for true (1) or not true (0), which allows computers to deal with Boolean logic." (White, 2008) Transistors can be combined into logic gates which then handle Boolean logic.   A transistors smaller size and less heat buildup, is the crucial event in history that changed computing.   This text from About.com by Mary Bellis, details the evolution of the transistor, "The transistor is an influential invention that changed the course of history for computers. The first generation of computers used vacuum tubes ; the second generation of computers used transistors; the third generation of computers used integrated circuits ; and the fourth generation of computers used microprocessors ." (Bellis, 2010).  

Photo - 1947 First transistor           Photo - Jack Kilby, Integrated Circuit 1958                                

Do you see the evolution link?

• Punch Cards/Gears levers/Vacuum Tubes
• Drum Memory/Magnetic Tape
• Core Memory
• Transistorized Memory
• RAM

 Please see this detailed chart. A History of Information Technology and Systems It gives a great timeline of the evolution of computer systems and storage devices.

Here is a link to How Ram Works: http://www.howstuffworks.com/ram.htm

Here is another link on How Computer Ram Works: http://www.articlesbase.com/hardware-articles/how-computer-ram-memory-works-716360.html

 Test Yourself !

Important Dates in Computer History:

1801   Joseph Marie Jacquard improved upon a textile loom by introducing a series of punch card paper templates, which allowed the loom to weave intricate patterns automatically.

1833   Charles Babbage constructs the first punch card machine with a memory store called the Analytical Engine . This machine used gears and levers and was programmed by punch cards.This difference engine could solve polynomial equations.

1932   Gustav Tauschek builds first drum memory.

1936   Konrad Zuse builds a mechanical calculator called the Z1.The Z1 was known as the world's first binary computer. Zuse focused on three major elements a calculating device should have.

1. A control
2. Memory
3. Calculator

The Z1 had an electrical engine and was programmed by punch tape. The Z2 had electrical relays and was known as the first electro mechanical computer. The Z3 had micro sequencers and used film tape instead of punch cards.

1946   Mauchly and Eckert develop the Eniac I (Electro Numerical Integrator and Calculator). The Eniac weighed 30 tons! It used Vacuum tubes, relays and switches.

1947   Fredrick Viehe , An Wang and Kenneth Olsen independently invent the magnetic core memory.      

          Jay Forrester develops the magnetic random access coincident-current drum.

1951   First commercial computer, The Ferranti Mark I . It had a 256 40-bit main memory and magnetic tape storage.

1952   The Edvac computer is created with 1024 44-bit words of ultrasonic memory. The Eniac gets a core memory device.

1954    First mass production of the IBM 650 magnetic tape data storage drum. First commercial ferrite-core memory.

1961    IBM 1401 magnetic core memory series. First transistorized 64-bit memory computer with memory protection and interleaving.IBM 7030 Stretch 64-bit data word and 32/64-bit instruction word computer.

1962   Atlas virtual memory

1965    British computer scientist Maurice Wilkes develops the idea of a cache computer memory. First integrated circuit random access memory application based on Read Only Memory ROM.

1968    Data General launches the 32-kilobytes memory Nova. Analog and digital memory are integrated on one chip by Dedicated Current Source. Robert Dennard invents and patents his Dynamic Random Access Memory DRAM. 

1969    Intel creates a 1 Kilobyte RAM chip. (Core Killer)

1970   First generally available Dynamic RAM 256-bit programmable semiconductor memory chip, the Intel 1103i. MOS Dynamic RAM is invented.

Computer memory timeline links: http://inventors.about.com/od/rstartinventions/a/Ram.htm

More detailed timeline information: http://www.lodbrok.be/refpages/timeline.htm

Important Machines in History That Used Memory

Test Yourself! 

Different Types of Ram

We have covered RAM, SRAM and DRAM. There are other types of RAM with distinct properties and differences. Some types you may know, DDR RAM, EDO RAM etc. Here is a link to help you learn the differences of these types of RAM.

http://www.computermemoryupgrade.net/types-of-computer-memory-common-uses.html

http://www.webopedia.com/quick_ref/dram_memory.asp

In conclusion, my main desire is to highlight major technology advancements in the history of RAM. Mary Bellis outlined the importance of the transistor as being crucial to the growth of electronic computing. I agree with her statements. I believe that the inventions by Forrester, Olsen, Wang and Veigh created the most reliable, efficient and cost effective electronic memory which became Random Access Memory. The Inventors.About.Com web article" History of Computer Memory", cites these inventors as being pivital in the creation of modern day computer memory. I agree with web articles findings.

Quiz Time ! 

 Click the red deck of cards to start.

References

Books: 

White, Ron.(2008).How Computers Work. 9th. IN: QUE Publishing 9. Print.

Websites:

Bellis, Mary, NP, web. History of Computer Memory, Retrieved from About.Com Guide, Inventors.http://inventors.about.com/library/weekly/aa050298.htm.

Bellis, Mary, NP Web The History of Vacuum Tubes. Retrieved from http://inventors.about.com/od/uvstartinventions/a/Vacuum_tube.htm

Binary Code: Retrieved from Wikipedia.http://en.wikipedia.org/wiki/Binary_code.

Butler, Jeremy G.(1997) A History of Information Technology and Systems.Retrieved from www.tcf.ua.edu/AZ/ITHistoryOutline.htm

Computer Memory Timeline: Timeline-Help.Retrieved from http://www.timeline-help.com/computer-memory-timeline-3.html.

Computing Timeline: Retrieved from http://www.lodbrok.be/refpages/timeline.htm.    

How Computer Ram Works: Article Base.com, NP, Web 2005-2010.Retrieved from http://www.articlesbase.com/hardware-articles/how-computer-ram-memory-works-716360.html.

How Stuff Works-RAM: How Stuff Works Inc.(1998-2010). Retrieved fromhttp://www.howstuffworks.com/ram.htm.

Inventors of the Modern Computer: About.Com Guide, Inventors. NP, Web 10/1/2010 Retrieved from http://inventors.about.com/library/weekly/aa060998.htm.

Konrad Zuse- Introduction: Retrieved from http://user.cs.tu-berlin.de/~zuse/Konrad_Zuse/en/konrad_zuse.html.

Ram: Quin Street Inc. (2010). Retrieved from Webopedia, About Internet.Com,http://www.webopedia.com/TERM/R/RAM.html.

Random Access Memory: Wikipedia NP, Web Retrieved fromhttp://en.wikipedia.org/wiki/Random-access_memory.

The Babbage Engine: The Computer History Museum. NP,Retrieved from http://www.computerhistory.org/babbage/howitworks/.

The History of Computer Memory, About.com, Inventors. NP, Retrieved from http://inventors.about.com/library/weekly/aa060998.htm.  

Video:

1950's Early mechanical "Direct Access" Drum Memory Storage. You Tube Video. Retrieved from You Tube http://www.youtube.com/watch?v=eIpoA7Ir9p8. 

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