or, Bob Braden USC/ISIbraden/myfiles/50years.slides.pdf · 21 Sept 01 Braden 1 Digital Computing in...

21 Sept 01 Braden 1

Digital Computing in 1951or,

“How I Spent my Summer Vacation”

Bob Braden

USC/ISI

21 Sept 01 Braden 2

Why 1951?

• Exactly 50 years (half century) ago (Century >> 1)

• A watershed year in the history of digital computing

– Externally-programmed machines---> stored program machines

– Electro-mechanical machines (counter wheels & relays)---> vacuum tubes

– One-of-a-kind machines ---> production machines

21 Sept 01 Braden 3

How was Computing Done in 1951?

• Scientific & engineering computation used:– Books of tables

– Mechanical desk calculators

– Slide rules

– Punched card equipment

– Large-scale automatic calculators

• Business computing used:– Mechanical desk calculators

– Punched card equipment

21 Sept 01 Braden 4

Overview of Talk

• Pre-1951– Scientific computing with punched cards

– Early automatic calculators

• 1951: Automatic Calculators– Electronic punched card equipment

– SSEC

• 1951: Electronic Computers– State of the art in hardware & software

– IBM 701

• Wrapup -- later developments

21 Sept 01 Braden 5

Scientific Computing with Punched Cards

• Scientific and engineering computation made extensive useof punched card equipment in 1930s, 1940s, and 1950s.

• Nurtured by IBM center at Columbia University

• Here “programming” => plugging wires intointerchangable plugboards

• Sort of “logical Lego” -- rather a fun puzzle.

• Some complex problems used 20 different plugboards.

• Sometimes needed to know details of machine logic & timing.

and operator instructions.

21 Sept 01 Braden 6

Example: Large plugboard...

Example of upper limit of plugboard complexity(Only top half is shown)

Most lines represent 5 - 11 wires each; ~ 260 wires total

21 Sept 01 Braden 7

Timing of plugboard hubs

Typical plugboard timing chart...

21 Sept 01 Braden 8

Operator Instructions: sample

• “ Integration of the Differential Equation d2P/dr2 = P* F(r) Using the Type601 Multiplying Punch”, P. Herget, Proc Scientific Comp Forum, IBM, 1948.

• Start with stacks of salmon, blue, green, and manila cards.

• On one cycle, [the operator] performs the following ... operations:

– 1. The salmon card is allowed to fall into the stacker.

– 2. The blue card is allowed to fall into the stacker.

– 3. The top card from the blue pile is picked up and held in one hand.

– 4. The first green card is allowed to fall into the stacker.

– 5. The second green card is placed behind the blue card being held...

– 6. The top card from the green pile is picked up and placed behind theother cards held in one hand.

...

– 11. The last salmon card is placed (in the direct position) ahead of allcards being held in one hand, and

– 12. This deck is now placed in the feed hopper to begin the next cycle.

21 Sept 01 Braden 9

Scientific Computing with Punched Cards

• Punched Card Machines:

– “Accounting Machines”• Read cards, Add/subtract using electro-mechanical counter wheels,

and print results. Add time ~ 400ms

– “Multiplying Punches”• Plugboards: program limited sequence of + - * /; repeat & test

• Multiply time ~ 2-5 sec

– Keypunches, sorters, collators, reproducers, ...• Create, sort, interleave, copy, ... card decks

( Approx 0.5 micro-MIPS)

21 Sept 01 Braden 10

Punched Card Example

Soft X-ray scattering from a solid at small angles

– Use IBM 602A multiplying punch --electro-mechanical

– Read a, b, c, d from a card, compute, and punch result: sqrt(a*(b-c)+ sqrt(4*(b+c)*2 + d/3.675))

– Used Newton-Rapheson iteration for each sqrt()

– Took ~2 minutes (chirping & clicking!) per card.

– 2 days to set up and test plugboard


Automatic Calculators before 1951

• 19th Century: Babbage’s Analytical Engine

• 1930s (pre-WW II)

– John V. Atanasoff, Iowa State• Vacuum tubes, rotating capacitive memory (D-R-RAM!)

– Konrad Zuse, Germany• Relays

– George Stibitz, Bell Labs• Relays

These have been thoroughly chewed over by books andarticles...


Large-Scale Auto Calculators in 1951

• Consider those built/under construction in 1951.

• Ignore UK developments and many secondary efforts.

• Distinguish:

(1) Automatic calculators

Externally programmed using paper tape orpunched cards or plugboards and switches...

(1a) One-of-a-kind large-scale calculators

(1b) Electronic punched card machines

(2) Large-scale electronic computersStored program (“Von Neumann machines”)


Automatic Calculators: 1951

MACHINE WHO WHENEXTERNALPROGRAMMING

TECHNOLOGY WORD SIZE

MEMORYWORDS

ADD TIME

MULTIPLYTIME (max)

Mark IASCC Harvard 1943 24 col PT 2200 ctr wheels

+ 3300 relays 23D+S 72 (ctr wh) 300 ms 6000 ms

Mark II Harvard 1948 TTY PT 13000 relays10D+S+5exp

96(relays) 200 ms 700 ms

Mark III Harvard 1952 Mag tape 4500 VT 16D+S 4350(drum) 4 ms 12.75 ms

ENIAC U Penn 1946 Plug wire,switches 19000 VT 10D+S 20 (ctr) 0.2 ms 2. ms

SSEC IBM 1948 80 col PT 12000 VT+ 21400 relays 19D+S 150

(relays) 0.3 ms 20 ms

IBM 604 IBM 1948Punchedcards 1400 VT 8D+S ~ 4 0.5 ms 12.5 ms

IBM CPC IBM 1949Punchedcards

VT (604) &Ctr wheels 10D+S

< 100 (ctr wh)

400 ms (FP)

400 ms(FP)


Electronic Punched Card Equipment

• 1948 IBM 604 “Electronic Calculating Punch”• The first mass-produced electronic calculator: 5600 built.

• Plugboard with 60 program steps + - * / , repeat, test.

• Technologically: miniaturized, cleverly packaged ENIAC

Both added by counting pulses;ENIAC: 1 digit = ring ctr of 10 FFs, 604: bcd (1248) ctr of 4 FFs.

ENIAC

The Origins of Digital Computers, Randall Ed., Springer-Verlag, 1975, p 232.

IBM 604


Electronic Punched Card Equipment

• 1949: IBM Card Programmed Calculator (CPC)• Technological kludge, but ~ 700 built, especially for So Cal

aerospace, research labs, universities.

• Several IBM punched card machines cabled together.

– 604: plugboard wired as calculator, 10digit floating point.

– Accounting machine to read instruction cards and printresults; 3 address instructions, one per card.

– Storage units using counter wheels < 100 #s

– To program a loop: feed same card deck through again...!

The Origins of Digital Computers, Randall Ed., Springer-Verlag, 1975, p 232.


IBM SSEC -- 1948

• Selective Sequence Electronic Calculator

• TJ Watson: ‘...come up with a “Super Calculator” thatwould eclipse the Harvard machine and consign it totechnological oblivion along with any likely offspring’. C. J. Bashe, Annals of History of Computing Oct 82.

• SSEC: ambitious in size and complexity;‘... Capable of solving problems far too large for anyother machines in existence in 1948.’ C. J. Bashe, ibid.

SSEC IBM 194812000 VT+ 21400 relays

19D+S 150(relays)

20 ms 20 ms

Mark IASCC Harvard 1943

2200 ctr wheels+ 3300 relays 23D+S 72 300 ms 6000 ms


IBM SSECPublic showcase: The SSEC wasbuilt into walls of a large room(1800 sq ft), with a plate glasswindow on 57th st & MadisonAve, NYC, next to IBMWorld HQ.

Lots of dancing lights andspinning tapes were visible...But when the machine was down,they drew the curtains!

SSECA Computer Perspective, C. & R. Eames, Harvard U Press, 1973


Official SSEC Picture

TJ Watson hated the pillars, so they magically disappeared!

IBM Corp., 1948


SSEC Control Console

T. J. WatsonNow THAT is a proper computer console !!


SSEC

• Conservative , transitional technology -- Relay memory but vacuum tube arithmetic unit.

• Memory hierarchy:

– Vacuum tube memory: 8 words

– Relay memory: 150 words

– Paper tape and cards: indefinite

Part of Arithmetic Unit

2 digits (8 FFs)


SSEC

• Eccles-Jordan 4 bit counter with feedback to count to 10


SSEC

• Instruction word size same as data word size = 20 digits;instructions fetched over data paths.

• Externally programmed, but could compute nextinstruction.

• 3 + 1 address instructions

• Instructions normally read from paper tape loops:

• Paper tape used IBM card stock, so 1 row held 80 punches(bits).


SSEC: Tape Memory Unit

Each subroutine used a separate tapeloop. Program execution was visiblein the spinning tapes...

And this is the machine that madethe program tapes...


(almost) Real Sample of SSEC code

Iterate: ;Q�� &�� $ ;

Q ��%� �VTUW�;

Q��

��XQWLO�DEV�;Q��;

Q��;

Q��

A separate tape loop has iterately computedsqrt(Xn) and left result in relay memory location 129.

Op First Second Result Shift COMMENTCode Operand Operand

EM RM EM RM EM RM

15 3 120 5 129 1 021 10R B * sqrt(Xn)

02 1 000 2 612 4 022 + 1/4

EM=electronicmemory

RM= relaymemory

Use value saved inelectronic memory

20 digits

Multiply

Add


(almost) Real Sample of SSEC codeOp First Second Result Shift COMMENTCode Operand Operand __________ __________ _________ S EM RM S EM RM EM RM

15 3 120 5 129 1 021 10R B * sqrt(Xn)

02 1 000 2 612 4 022 + 1/4

15 3 011 5 128 1 023 10R A * Xn

15 1 000 4 000 5 126 *

15 3 613 5 000 1 194 * 1/12

02 1 000 2 121 5 167 + C -> Xn+1

02 5 000 - 6 000 2 044 Xn+1 - Xn

04 ------ 5 000 1 100 5R Xn+1/10**5 = tol.

02 1 000 -abs 2 000 3 158 19R (Shift off all but sign)

02 ------ 6 127 6 128 Xn+1 -> Xn

(Sign in 158 selects next instruction:if -: repeat loop; else: proceed to next)

Sqrt tape

Repeat

Next

Tapeloop


SSEC Significance

• Completed ~30 problems over its 4 year lifetime.

– Planetary orbits, fluid flow, atomic fields, optics,ordinance, hydrodynamics, ...

– Included one large classified problem for AEC/LANL.

• SSEC was a technological brontosaurus; no significanteffects on later machines.

• SSEC did “star” in one movie: “Walk East on Beacon”

• SSEC helped shape the popular image of a “Giant Brain”


Large-Scale Electronic Computers: 1951

MACHINE WHO WHEN TECHNOLOGY WORD SIZE

MEMORY ADD TIME

MULTTIME

EDSAC Cambridge19493000 VT,serial

36b512(HgDL)

1400 us 5400 us

EDVAC U Penn 19513600 VT,serial 44b

1024(HgDL) 846 us 2900 us

Univac IRemingtonRand 1951

?? VT, serial

12 DD(7b chars)

1000(HgDL) 525 us 2150 us

IAS Inst AdvStudy

1952 VT, parallel 40b 4096(CRT')

62 us 713 us

IAS clones (various) later VT, parallel 40b4096(CRT)

IBM 701 IBM 1952 VT, parallel 36b4096/8192(CRT) 60 us 456 us

Important stored program machines built/under construction


Large-Scale Electronic Computers: 1951• Exploring the design space:

– Binary or decimal radix

– Serial or parallel arithmetic logic

– Various word sizes

• Hardware features invented but not yet available in US:

– Floating point

– Index registers

• Building an arithmetic engine using vacuum tubes was astraightforward engineering problem.

• The BIG technical problem was memory!


Memory Technologies, 1951• Acoustic (Hg) delay lines

• Circulate acoustic pulses through Hg column

• Store 400 - 800 bits in column. Latency ~ 400 usec

• Alan Turing suggested gin (H20 & alcohol)

• CRTs: dynamic capacitive memories• Secondary electrons create potential wells on tube face

• Semi-transparent conductive surface on outside face of tube

• Periodically read & dynamically regenerate

• Magnetic drums

Best guess: would need 4K words for most problems.


Computer Hardware Reliability: 1951

• Hardware reliability was a BIG problem in 1951!!

• Electromechanical devices were flaky, of course.

• Vacuum tubes often failed in on/off operation.

• In early machines, CRT memory failures could beprogrammed!– “Read-around ratio”

(how often can readone spot before surroundingspots are compromised.)Tight loops were BAD!

• Early magnetic drums were flakey, too! CRT face with raster of 1s, 0s

40 bits

32words


Computer Hardware Reliability: 1951

• CRT memory on IBM 701 largely solved read-aroundproblem by interleaving addresses, but still requiredfrequent critical adjustment. MTBF 10 mins to 8 hrs.

• 1951 programmers had to expect machine errors=> Had to program extensive checking, duplicatecalculations, elaborate checkpoint/restart code.

• Core memory and better vacuum tubes (and latertransistors) cured the reliability problems within a fewyears.


Computer Software: 1951

• Programming basics well understood --

– Basic treatise: Wilkes, Wheeler & Gill, “Programming for anElectronic Digital Computer”, Addison-Wesley, 1951.

• Parametrized subroutines

• Subroutine libraries [on paper tape/punched cards]

• Relocating loaders

• Interpreters

• 2-3 years in future:

– Fully symbolic assemblers

– Fortran

• Programmers ~ mathematicians


Large-Scale Electronic Computers: 1951

MACHINE WHO WHEN TECHNOLOGY WORD SIZE

MEMORY ADD TIME

MULTTIME

EDSAC Cambridge19493000 VT,serial

36b512(HgDL)

1400 us 5400 us

EDVAC U Penn 19513600 VT,serial 44b

1024(HgDL) 846 us 2900 us

Univac IRemingtonRand 1951

VT, serial

12D(7b chars)

1000(HgDL) 525 us 2150 us

IAS Inst AdvStudy

1952 VT, parallel 40b 4096(CRT')

62 us 713 us

IAS clones (various) later VT, parallel 40b4096(CRT)

IBM 701 IBM 1952 VT, parallel 36b4096/8192(CRT) 60 us 456 us

Important stored program machines built/under construction


Parallel Binary Computers

• IAS (Institute for Advanced Study) Computer 1952

– Seminal machine, built at IAS to design by Von Neumann & Goldstein.

• IBM 701: “Defense Calculator” 1952

– Elegantly engineered and packaged realization of VonNeumann’s IAS design.

– Two one-address instructions per word

– Minimalist op code set


IAS Computer 1952John Von Neumann in front of IAS (Institute for Advance Study) Computer

A Computer Perspective, C. & R. Eames, Harvard U Press, 1973


From 1/Kind Computers...Manchester Univ Mark I --1949

IAS Machine 1952

SEAC 1950

Early British Computers, Lavington, Manchester U Press, 1980, pp 38-39




... To Production Computers

IBM 701 -- “Defense Calculator”

Boxes rolled on wheels; cabled together under the raised floor


.

IBM 701 installed at IBM WHQ, NYC, 1952

(The same room that held the SSEC)


IBM 701 Programming

• 701 was designed as a commercial product: clearlydocumented, careful human engineering.

• WW&G’s programming notation was at best obscure!

• IBM foresaw that some programmers might not be graduatemathematicians.

• Programming technology: taken straight from Wilkes,Wheeler, & Gill (EDSAC/EDVAC)

• Subroutines

• Relocating loader

• Regional assembler


701 Software

• Dedicated machine -- no OS of any kind!

– Read card deck: bootstrap loader, assembler, sourceprogram, data.

– Had to manually splice magnetic tapes onto leaders

• Debugging Tools:

– Octal memory dump to printer

– Tracing

• We really DID stick chad back into punched cards to makebinary patches!

• There was also a floating point interpreter (Speedcode)(written by ex-SSEC staffer John Backus)


Regional Assembly Language: IBM 701'R� ;Q�� & � �� $ ;Q �� % VTUW� ;Q ��

XQWLO DEV�;Q�� ;Q� � �;Q��

07F 0000 + ADD 00A 0001 Save exit address07F 0001 + STORE A 07F 002307F 0002 + TR 35F 0000 A(sqrt subroutine)07F 0003 + STOP 00N 0002 A(Xn)07F 0004 + STOP 00N 0004 A(Xn+1)07F 0005 - LOAD MQ 00K 0102 Get B07F 0006 - MPY ROUND 00N 0004 * sqrt(Xn)07F 0007 - ADD 00K 0006 + 1/407F 0008 - STORE 00N 000007F 0009 - LOAD MQ 00N 0002 Xn07F 0010 - MPY ROUND 00K 0100 * A07F 0011 + L RIGHT 000 0035 AC -> MQ07F 0012 - MPY ROUND 00K 0008 * 1/1207F 0013 + L RIGHT 000 0035 AC -> MQ07F 0014 - MPY ROUND 00N 000007F 0015 - ADD 00K 0104 +C07F 0016 - STORE 00N 0006 = Xn+107F 0017 - SUB 00N 0002 - Xn07F 0018 - STORE 00N 0008 save diff07F 0019 - R SUB 00N 0006 - Xn+107F 0020 + A RIGHT 000 0015 >> 15 = tolerance07F 0021 - ADD ABS 00N 000807F 0022 + TR + 07F 0002 Go around loop again07F 0023 + TR 000 0000 (exit)

Relocatable (specifies “region ”)or zero (absolute)


1954: Future Rumors...

• ... That John Backus was leading a group to develop aprogram that could write (efficient) programs, givenalgebraic statements. [I found this hard to believe...!]

• ... That IBM was developing a machine with new memorytechnology (magnetic cores) that could run for months oreven (gasp) years without dropping a bit!

• ... That the 704 designers had developed a truly symbolicassembler.


701: Beginning of a Computer Dynasty

• Beginning of the IBM 36-bit computer dynasty...

– 701: CRT memory, basic VonN/IAS design

– 704: Core memory, 3 index registers and floating point

– 709: Added channels (i.e., DMA I/O)

– 7090: Transistorized

• Parallel development of decimal business computers

– IBM 702, 705, 650, 1401, ...

• And there were all the other computer companies...


Later Developments

Later software developments:

• Indirection, pointers

• Stacks and queues

• List processing

• Operating systems

• The word “software”

• Computer Science

1951 was just the beginning of the computerstory, but this is the end of this talk!

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