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|Manufacturer ||University of Pennsylvania |
|Identification,ID ||- |
|Date of first manufacture||- |
|Number produced ||- |
|Estimated price or cost||- |
|location in museum ||- |
Contents of this page:
- 20 individual 10 digit accumulators.
- Accumulators can transmit numbers to other accumulators through the digit
output terminals labeled A (for add) and S (for subtract).
- Similarly, accumulators can receive numbers through 5 digit input terminals,
labled Alpha, Beta, ...
- Timing for transmission and reception of numbers is controlled by pulses received
by the program pulse terminals. Each accumulator has twelve program controls.
On each accumulator, Program Controls 1--4 are non-repeat controls that perform
only one function when they receive a pulse on their program input terminal.
Program Controls 5--12 are repeat program controls that can perform the same
function up to nine times. A repeat program control begins to perform when it
receives a pulse on its input terminal. When it is finished, it transmits a
pulse on its output terminal
- 10's Complement Negative numbers are stored in the Eniac by their
10's complement which is computed by subtracting a given number from
M 9 999 999 999 and then adding one. For example, to find the way -84
is represented, we perform the subtraction:
M 9 999 999 999
- P 0 000 000 084
M1 9 999 999 915
We then add one, to get our result -84 = M 9 999 999 916
- 1 multiply unit
- 1 divide unit
- 1 square root unit
- 3 function generators
- All of the above units could be wired (programed) to function in parallel
- The most important technical achievement of the Eniac was its lightning speed.
The Eniac takes only 200 microseconds to add or subtract.
That means that it can perform 5000 addition cycles each second.
- Another significant feature of the Eniac is its ability to perform digit discrimination
and branch loops. The Eniac was the first machine to support common
``if statements'' that are so vital to the execution of useful programs.
- Despite all its similarities to today's computers, the Eniac maintains some
important differences. The main one is that it can not store its programs
electronically. Programs must be hard-wired before the machine is started.
The other interesting difference is that the machine is ``synchronous.''
The timing of all instructions is set up before a program is begun.
A Short History of the Second American Revolution states that the
mean time between failures was greater than 12 hours, This was gained by"
- Lower power levels and careful design alternatives were sought to minimize
the amount of work demanded of the vacuum tubes.
- Most tubes were found to fail early or late in their lives,
which resulted in a regimen of preventive maintenance ensuring that only the
healthiest" tubes were used in the ENIAC.
- Eckert instituted rigid requirements for careful design and construction that
had to be met by all engineers and technicians on the project where even a
faulty soldering joint could render the entire machine useless.
- Universal design standards, established collaboratively by all of the Moore
School engineers ensured that components such as resistors, as well as the
vacuum tubes, operated at a certain percentage of their rated capacity. "
- from alt.folklore.computers "According to the official specs, the ENIAC used
17,468 tubes, but only 16 different types of tubes. (as reproduced in
Nancy Stern's "From ENIAC to UNIVAC" for whatever it is worth)."
At some later date, ENIAC was converted to a stored program machine.
- This unit is one of the twenty accumulators. there were also other types of units such
as a multiplier, 3 function generators, and switch input panels. The whole unit filled
a very large room, and had 18,000 vacuum tubes.
Interesting Web Sites
- If you feel threatened by assembly language programming,
you would go crazy "programming" an ENIAC.
- Two of the 6 original ENIAC programmers spoke at the 2000 ACM Awards Banquet
- Kathy Kleinman of the ACM (legal staff?) is writing a book,
and has a large number of high quality photographs
- pieces of ENIAC at ?
- Arthur Burkes - computer science? - has 4 accumulators
- Univ of Penn
Smithsonian - has enough to do a demo
- West Point
- University of Michigan (Ann Arbor) EECS building
- The Eckert estate was auctioned off by Skinner of Boston. There was
apparently a piece(s) of the Eniac.
News group alt.folklore.computers had "Philadelphia Inquirer for Friday, April 28, 2000,
page E8, reports that the lot was sold at the Skinner auction for $79,500,
but does not state who was the buyer."
- "ENIAC" by Scott McCartney, (reviewers say very non-technical, newspaper like)
If you have comments or suggestions, Send e-mail
to Ed Thelen
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Updated May 14, 2012