Loadstar 245/245.d81/t.eniac

Text File | 2022-08-26 | 12KB | 424 lines

u
       AN INTERVIEW WITH ECKERT
         by Alexander Randall


    There are two epochs in computer
history:

    Before ENIAC and After ENIAC.

The first practical, all-electronic
computer was unveiled on Feb. 14,
1946, at Pennsylvania University's
Moore School of Electronics. While
controversies continue about who
invented what, most can agree that the
ENIAC (Electronic Numerical Integrator
And Computer) serves as the watershed
project, showing that electronic
computing was possible. It was a
masterpiece of electrical engineering,
with unprecedented reliability and
speed. The two men most responsible
for its success were J. Presper Eckert
and John W. Mauchly.

    I recorded two days of interviews
with "Pres" Eckert in 1989. He was 70
years old. My father was Pres' best
friend from childhood and I'd spent my
childhood playing with his children. I
visited him regularly as an adult. On
that day, we spoke in his living room
in Gladwyne, PA, most of the time
sitting on the floor. We stopped
talking about computers only to fiddle
with his Nova Chord electronic organ,
which predated ENIAC, and we fiddled
with stereo speakers. On a second
occasion I recorded a conversation at
his daughter's home in western
Massachusetts. Eckert died in 1995.
I've had the interview tapes for many
years, but decided to transcribe them
for ENIAC's 60th anniversary.


[How did calculating machines work]
[before ENIAC?]

    Well, a person with a paper and
pencil can add two 10-digit numbers in
about 10 seconds. With a hand
calculator the time is down to 4
seconds. The Harvard Mark 1 was the
last of the electro-mechanical
computers -- it could add two 10-digit
numbers in 0.3 seconds, about 30 times
faster than paper and pencil.

    When I was a graduate student, the
Moore School of Electronics had two
analyzers that were essentially copies
of Vannevar Bush's machine from MIT.


[What could that machine do?]

    It could solve linear differential
equations, but only linear equations.
It had a long framework divided into
sections with a couple dozen shafts
buried through it. You could put
different gears on the shafts using
screwdrivers and hammers and it had
"integrators," that gave the product
of two shafts coming in on a third
shaft coming out.

    By picking the right gear ratio
you should get the right constants in
the equation. We used published tables
to pick the gear ratios to get
whatever number we wanted. The limit
on accuracy of this machine was the
slippage of the mechanical wheels on
the integrator.

    That made me say, "Let's built
electronic integrators and stick them
into this machine instead of those
wheel things." We added several dozen
motors and amplifiers and circuits
using over 400 vacuum tubes, which, as
electronic things go, is not trivial.
The radio has only five or six tubes,
and television sets have up to 30. The
Nova Chord organ was built prior to
this and it has about 170 tubes. The
Bush Analyzer was still essentially a
mechanical device.

    That led me to examine if I could
find some way to multiply pulse
numbers together so I didn't need
gears -- then I could do the whole
thing electrically. There's a theorem
in calculus where you can use two
integrators to do a multiplication. I
talked with John Mauchley about it.
Just who put in which part is hard to
tell, but the idea of doing the
integrations by counters was mine.

    The ENIAC was the first electronic
digital computer and could add those
two 10-digit numbers in 0.0002 seconds
-- that's 50,000 times faster than a
human, 20,000 times faster than a
calculator and 1,500 times faster than
the Mark 1. For specialized scientific
calculations it was even faster.


[So it's a myth that ENIAC could only]
[add, subtract, multiply and divide.]

    No, that's a calculator. ENIAC
could do three-dimensional, second-
order differential equations. We were
calculating trajectory tables for the
war effort. In those days. The
trajectory tables were calculated by
hundreds of people operating desk
calculators -- people who were called
[computers]. So the machine that does
that work was called a computer.


[So what did they give you? Did they]
[say, "Here's a room, here are some]
[tools, here are some guys -- go make]
[it?"]

    Uh-huh. Pretty much.


[What did ENIAC's room look like?]

    We built ENIAC in a room that was
30 feet by 50 feet, at the Moore
School in West Philadelphia on the
first floor.


[There's a story that ENIAC dimmed]
[the lights in Philadelphia when it]
[was in use.]

    That story is total fiction,
dreamed up by some journalist. We took
power off of the grid. We had voltage
regulators to provide 150 kilowatts of
regulated supply.


[Did the military guys working on]
[ENIAC salute the machine?]

    Another ENIAC myth.


[You said the largest tube gadget in]
[1943 was the Nova Chord electronic]
[organ. What did ENIAC use?]

    ENIAC had 18,000 vacuum tubes. The
tubes were off the shelf; we got
whatever the distributor could supply
in lots of a thousand. We used 10 tube
types, but could have done it with
four tube types; we just couldn't get
enough of them. We decided that our
tube filaments would last a lot longer
if we kept them below their proper
voltage. Not too high or too low. A
lot of the circuits were off the
shelf, but I invented a lot of the
circuits as well. Registers were a new
idea. So were integrator circuits.

    The function of the machine was
split into eight basic circuit
components: the accumulator,
initiator, master programmer,
multiplier, divider/square-root, gate,
buffer, and the function tables. The
accumulator was the basic arithmetic
unit of the ENIAC. It consisted of 20
registers, each 10 digits wide, which
performed addition, subtraction and
temporary storage. The accumulator can
be compared to the registers in
today's central processing units.


[Are there any of your circuits]
[still in use in today's personal]
[computers?]

    No, but that's true of any first
invention. Edison's original light
bulb bears no resemblance to a modern
bulb. They do the same thing but with
totally different components. Same
with the computer. What did survive
were the concepts, not the hardware.

    The idea of a subroutine was
original with ENIAC. Mauchly had this
idea based on his knowledge of the
inner workings of desk calculators and
introduced me to his idea for a
subroutine in the machine. On Mark-1,
if they wanted to do a calculation
over and over they had to feed the
same tape in over and over. We
invented ways to run the same
subroutine without any mechanical
input. The idea of using internal
memory was also original with ENIAC.


[There is a story that there was a]
[guy running around with a box of]
[tubes and had to change one every]
[few minutes.]

    Another myth. We had a tube fail
about every two days and we could
locate the problem within 15 minutes.
We invented a scheme to build the
computer on removable chassis --
plug-in components -- so when tubes
failed we could swap them out in
seconds. We carried out a very radical
idea in a very conservative fashion.


[How many people were working on]
[ENIAC?]

    Total count was about 50 people,
12 of us engineers or technical
people. Mauchley was teaching
part-time, others had part-time jobs.
I was on it full-time as chief
engineer.


[How old were you?]

    We signed the contract on my 24th
birthday: May 9, 1943.


[Was ENIAC programmable?]

    Yes and no. We programmed the
machine by plugging wires in from
place to place. That's not hard-wired;
it's not software; it's not memory.
It's pluggable programming. And we had
switches to set the functions.


[What was the first thing you did]
[with ENIAC?]

    It was designed to calculate
trajectory tables, but it came too
late to really help with the war
effort. The first real use was Edward
Teller using ENIAC to do calculations
for the hydrogen bomb.


[What's the zaniest thing you did]
[while developing ENIAC?]

    The mouse cage was pretty funny.
We knew mice would eat the insulation
off the wires, so we got samples of
all the wires that were available and
put them in a cage with a bunch of
mice to see which insulation they did
not like.