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Innovative Ideas & Stepping Stones Part I

32K word magnetic core memory board

Magnetic core was the main memory in computers from about 1955 to the 1970s. This minicomputer memory combines core with integrated circuit (IC) drivers. ICs would soon replace the cores themselves.

Innovative Ideas & Stepping Stones

Necessity is the mother of invention. But not all her offspring end up equally successful.

Computer engineers recognized the need for efficient, reliable, affordable memory and storage. Many devised solutions, often attracting supporters who invested considerable money and time. Some ideas worked. Others fizzled, yet served as valuable stepping-stones to later technologies. And many, ultimately, proved creative dead ends.

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Transformer Read Only Storage (TROS) module

Each bit of this read-only memory for microcode is a little magnetic transformer. Punches in the mylar strips control whether current flows through the transformer or around it, representing a zero or a one.

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Core Rope Memory

Developed in the mid 1950s, core rope technology used a matrix of ferrite cores and wires for “read only” memory. Because it was relatively immune to electromagnetic interference, military and aerospace applications continued using rope memory into the 21st century.

Apollo Guidance Computer rope memory wiring

It could take days to change one line of a program stored in rope memory.

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Apollo Guidance Computer read-only rope memory

This rope memory, used on the Apollo Guidance Computer for the mission to the moon in 1969, was made by hand.

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Apollo 11 launch

The Apollo Guidance Computer — along with three astronauts — lifted off on July 16, 1969.

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Bubble Memory

Bubble memory—small, magnetized areas (“bubbles”) on a thin film—seemed a promising technology when Bell Labs first explored it.

By mid 1970s, nearly every major electronics firm was interested. An estimated $1 billion was spent on research. But, eclipsed by hard disk and semiconductor RAM in the 1980s, the bubble popped.

Intel Bubble Memory advertisement

Bubble memories were promoted as more robust than hard disks. They probably were, but they still did not succeed.

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4 Mbit bubble memory array

A few magnetic bubble memories reached the market and were used in video games and machine tool controllers. Each silver square on this board stores 1 Mbit.

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Charge-Coupled Storage Devices?

Charge-coupled storage devices failed. And then triumphed.

Developed at Bell Labs in the 1960s for solid-state storage, CCDs were swiftly surpassed by magnetic disks. They never succeeded as storage. However, astronomers recognized their potential as light sensors. CCDs became a mainstay of digital cameras—honored in the 2009 Nobel Prize in Physics.

Bell Labs researchers with charge-coupled device (CCD)

Willard Boyle (left) and George Smith demonstrate a video camera built using the CCD they invented. In 2009 they received the Nobel Prize for Physics.

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D-395 digital camera

The first commercial digital camera was sold in 1990. Charge-coupled devices (CCDs) have revolutionized photography and made photographic film largely obsolete.

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F460DC Charge-Coupled Device (CCD) memory chip

CCDs contain long rows of capacitive bins holding electrical charges that shift along the rows. This chip was just a shift-register memory. But if light focused on the bins creates the charges, a CCD becomes an image sensor.

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IBM 1360 Photo-Digital Storage System

Trillion-bit storage for the first time! An electron beam wrote bits onto small plastic film strips, which were stored in bins and managed by a complex robotic retrieval system. Difficult to keep running, only seven were produced—all for government customers.

IBM 1360 Photodigital Store

This massive archival storage system held about 160 GB. You now can carry that much data in your pocket.

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IBM 1360 ("Cypress") photo-digital storage system module

This terabit memory was inspired by a CIA project to store vast amounts of information.

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Thin Film Memory

Sperry Rand developed this faster variation on core memory. Small glass plates held tiny dots of magnetic metal film interconnected with printed drive and sense wires. Used in the 1962 UNIVAC 1107 for high-speed registers, it proved too expensive for general use.

Sperry Rand UNIVAC 1107 computer

The 1107 used thin film memory for its high-speed registers. Though touted as “the most significant technological achievement since solid-state circuitry,” it didn’t last long.

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Thin film memory

Although short-lived, thin film memory was used in some military computers because it was fast and resistant to radiation.

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RCA Selectron Tube

Jan Rajchman at RCA began work in 1946 on Selectron tube memory: vacuum tubes with isolated gates (“eyelets”) that stored individual bits. Complicated and expensive, Selectron tubes were used only in the JOHNNIAC…and later replaced even there with core memory.

JOHNNIAC in operation

JOHNNIAC’s main memory initially consisted of 80 expensive RCA Selectron tubes holding a total of 512 40-bit words.

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JOHNNIAC Selectron tube

Originally designed to hold 4096 bits, the tubes RCA could actually produce held just 256 bits. Each bit was as an isolated stored charge that was continuously regenerated.

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