1

Vacuum Tubes & TransistorsThe birth of the digital computer

Jenya PesinTal Sela

The Vacuum Tube Era

Edison’s light-bulb

1880

Edison’s light-bulb

• Edison experiments with incandescent lamps

• He notices an uneven blackening of the glass

1880

The Edison effect

1880

The Diode

• John Ambrose Fleming – first to put Edison’s ideas to

the test in a telegraph communication detector

• Allows current flow in only one direction

• Used to convert AC to DC

1904

2

DRL (Diode-Resistor Logic): OR

• If both inputs are held at logic ‘0’, output is held at logic ‘0’ by the ground

• Either input at logic ‘1’will make its diode forward biased and conduction will pull output up to logic ‘1’

DRL (Diode-Resistor Logic): AND

• Only if both inputs are held at logic ‘1’, neither of the diodes conduct, and the output is a logic ‘1’

• If either of the inputs are logic ‘0’, its diode will conduct and the resistor will pull down the output to a logic ‘0’

The Triode

• Lee de Forest invents the triode (“Audion”)• Used as a current amplifier

• Many improvements based on Fleming’s invention followed, creating new kinds of vacuum tubes– The tetrode (two grids)– The pentode (three grids)

1906

The Triode

1906

Triode NOR gate

• DRL is not a complete logic system!

• Possible solution: DRL and a triode NOT gate

• A better complete system:– a triode NOR gate 011

001010100

A nor BBA

NOR: A complete system

• Example – an AND gate:

10011

01001

00110

01100A AND BNOT BNOT ABA

3

ABC – Atanasoff-Berry Computer

• Built in Iowa state college• First electronic digital computing device• Solved problems with 29 linear equations• Not Turing complete• Total wire length: 1.6km• Weight 320kg• Vacuum tubes: 280• Not programmable

1942

ABC – Atanasoff-Berry Computer

• Implemented three critical ideas, a part of every modern computer:

• Binary digits represented data/numbers• Calculations with electronics, not mechanics• Separate computation and memory

• Controversy over “First computer”…• Won lawsuit against ENIAC and declared first digital

computer

1942

Colossus: The motive

• During WW2, German “Lorenz” machines were used to send encrypted messages.

• Colossus was built tohelp decipher “Lorenz”encoded messages.

• Emulated the “Lorenz”machine.

1944

Colossus

• First to use shift registers• First to introduce partial

programmability (by rewiring)

• Was never powered down unless malfunctioned

• Was kept secret!

1944

ENIAC: The reasons

• Helped in the design of the Hydrogen bomb• Ballistic calculations for large guns in WW2• A time consuming operation:

– A person: ~20 hours– Bush differential analyzer: ~15 minutes.– ENIAC: ~30 seconds

1946

ENIAC

Electronic Numerical Integrator and Computer• Built in the University of Pennsylvania.• First large scale computing device.• Partially programmable by rewiring• 17,468 Vacuum tubes, 7,200 diodes• Used decimal

representation• Weight: 27 tons

1946

4

EDVAC

Electronic Discrete Variable Automatic Computer• Built in the University of Pennsylvania.• Weight: 7.85 metric tons.• Size: 45.5 square m.

1949

EDVAC

• First programmable multipurpose computer

• More internal memory than any preceding computer (5.5KB in mode

• Total memory: 5.5KB (in modern terms)

• 6,000 Vacuum tubes, 12,000 diodes.

1949

Von Neumann architecture

• The early computers:– Have fixed programs.– Need rewiring in order to change the program

• In the Von Neumann computer– Single storage structure to hold instructions and

data– The instructions (program) are treated the same

way as data thus easily modified

1948

The Manchester SSEM

A working replica was built in 1998Small-Scale Experimental Machine, “The Baby”

1948

The Manchester SSEM

• First Von Neumann architecture computer

• SSEM determined the highest factor of 218 in 52 minutes…

• Input:by setting sequences ofbits at chosen addressesusing a simple keyboard

1948

The Manchester SSEM simulator

1948

5

EDSAC

Electronic Delay Storage Automatic Calculator

First “video game”(using ray tubes)

1949

EDSAC

• Built at the university of Cambridge• 3,000 vacuum tubesThe first program:

– Printed the squares of integers from 0 to 99…

• Was used to find the largest prime number of the time – 79 digits (!)

1949

1949, May 6th: Machine in operation for first time.Printed table of squares (0-99), time for programme 2 mins. 35 sec. Four tanks of battery 1 in operation

EDSAC accessories

Logbook

Input tape

Tape splicer

1949

EDSAC simulator

1949

UNIVAC - Universal Automatic Computer

• Developed by EMCC (Eckert-Mauchly Computer Corporation)

• First American commercial computer

• Weight: 7.25 metric tons• 5,000 vacuum tubes• 46 Machines sold overall

1951

UNIVAC

• Used to predict US 1952 elections• First to use magnetic tape output• 1000 calculations per second.

1951

6

IBM 701

The 11-part IBM-701

Drum memory

Card reader1953

IBM 701

• IBM’s first commercial scientific computer• Built to help the US government in the

Korean war• 16,000 addition/subtraction or 2,000

division/multiplication operations per second• Various IO mechanisms:

– Input: Punched cards, magnetic tapes– Output: Punched cards, printer

1953

WEIZAC - Weizmann Automatic Computer

• First Computer in Israel• Punch paper tape• 5 KB total memory

1954

WEIZAC

The console of the WEIZAC

The WEIZAC Console

The WEIZAC CPU

1954

The Transistor Era

P-N Junction

• Russell Ohl studying crystals in the Bell Labs

1939

7

P-N Junction

No current measured Current measured

1939

• Work on the P-N junction continued• First transistor invented at Bell Labs by

Bardeen and Brattain

The transistor

1947

The transistor

1947

The transistor

1947

The transistor

1947

The transistor

0V5V 1V

5V

8

The transistor

The first point contact transistor

1947

Why not point contact transistor

1947

• William Shockley invents the sandwich transistor

The transistor

1947

First sandwich transistor

The transistor

1947

• Easy to manufacture• More reliable

Using the transistor

Building a NOT gate using RTL(transistors and resistors)

E

C

Using the transistor

Building a NAND gate using RTL

EC

9

Early transistors

1947

More modern transistors

1947

• More reliable• Less space• Cheaper• Less power

Transistor – the reasons IBM 608

• First completely transistorized computer• 50% reduction in size • 90% reduction in power requirements • Cost: 83,210$

1955

IBM 7090

• General purpose transistor logic computer• Computing speed 5 times faster than the

vacuum tubes computers

1958

Bibliography

• http://www.play-hookey.com/digital/electronics/dl_gates.html• http://en.wikipedia.org/wiki/Thermionic_emission• http://www.allaboutcircuits.com/vol_3/chpt_13/2.html• http://www.jacmusic.com/html/articles/ericbarbour/howavacuumt

ubeworks.html• http://www.4p8.com/eric.brasseur/intvac.html• http://en.wikipedia.org/wiki/Diode_logic• http://www.quadibloc.com/comp/cp01.htm• http://en.wikipedia.org/wiki/Atanasoff-Berry_Computer• http://cs.ubc.ca/~hilpert/e/ABC/asm.html• http://en.wikipedia.org/wiki/Colossus_computer• http://en.wikipedia.org/wiki/ENIAC• http://en.wikipedia.org/wiki/EDVAC

10

Bibliography

• http://www.ece.umd.edu/~taylor/Electrons3.htm• http://www.comsci.us/history/gen1.html• http://www.computerhistory.org/timeline/?category=cmptr• http://www.thocp.net/hardware/univac.htm• http://wwwcsif.cs.ucdavis.edu/~csclub/museum/items/univac.ht

ml• http://www.cc.gatech.edu/gvu/people/randy.carpenter/folklore/v

5n1.html• http://www.davidsharp.com/baby/babyuserguide.pdf• http://www.cl.cam.ac.uk/conference/EDSAC99/reminiscences/• http://edsac.net/

Bibliography

• http://www.cl.cam.ac.uk/cgi-bin/relicd?name=&machine=EDSACI&class=any&uid=

• http://www.wisdom.weizmann.ac.il/weizac/weizac.html• http://www-

03.ibm.com/ibm/history/exhibits/vintage/vintage_4506VV2214.html

• http://www.columbia.edu/acis/history/generations.html• http://www-

03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP7090.html