5 ms·

ENIAC Operating Manual (1946) [pdf]

Mxtetris 7y ago
See also this work-in-progress ENIAC simulator: https://www.cs.drexel.edu/~bls96/eniac/ https://www.cs.drexel.edu/~bls96/eniac/
- segfaultbuserr 7y ago
  An interesting fact of ENIAC is, although it was originally programmed by plugboards in 1946, it was soon retrofitted to a stored-program computer in 1948 to simplify programming, using its spare function table units as ROM, and its extra accumulators as a program counter and a pointer. I wonder if there's any project to recreate an ENIAC simulation in stored-program mode.
  - hcs 7y ago
    For anyone interested in this period, there's a book on the stored-program ENIAC: http://eniacinaction.com/ http://eniacinaction.com/
andrewstuart 7y ago
The thing that people might find hard to understand these days is that computers - particularly mainframe or minicomputers - were really unreliable. The hardware was often/always custom built and it would often just stop and the manufacturer had to come in to work out what was wrong, and fix it which typically involved replacing boards until the problem went away. I should note that I'm basing this experience of being involved with company in the late 1980's - not the 1940's which is the topic of this post. Although I can imagine that back then the machines would only run for a matter of hours at best before breaking down and needing debugging. It was the same with networking which was particularly unreliable when it ran over coaxial cables like RG58 which had an array of problems that would lead to the whole company network going down and taking all the connected PCs with it. Modern computing is incredibly reliable.
- rootbear 7y ago
  The early, first generation tube-based computers had tube failures more or less daily. Higher reliability tubes specifically intended for computers were eventually introduced. One trick was to run the tube filaments "derated", or under the rated voltage. The tubes worked fine as logic elements at the lower voltage although that probably messed up their normal response curves. When I saw the Colossus rebuild at Bletchley Park, I asked about tube failure and they confirmed that they run the tubes (or valves, as they call them) on the Colossus at derated voltage, greatly reducing the failure rate.
- AnimalMuppet 7y ago
  My mother was a programmer in the 1950s. Someone came in early every morning and ran memory tests. If a tray of memory failed, they replaced it so that the computer could run while a tech debugged the failing tray. (A tray was 100 words by 36 bits of tube memory.)
  - dboreham 7y ago
    Same. Except my mother talks about replacing Valves (Vacuum Tubes).
    - hedora 7y ago
      When I visited the USS Hornet museum (WWII aircraft carrier docked in Oakland), our tour guide was the guy that used to replace vacuum tubes during combat. The targeting computer was analog, and controlled a very large anti aircraft gun using radar to to automatically track targets and compute parabolas. The gunner sat in a little control seat on the turret. When a tube blew, the whole turret would start oscillating violently. The job of our guide was to pull refrigerator-sized banks of vacuum tubes out of the wall, replace all the ones that looked dim, slam it shut, and move from bank to bank until it stopped trying to shake the poor gunner out of his seat. The shells had a timer inside them, and the people loading it had to set the delay between launch and detonation based on the time of flight the computer reported. The timer was actuated when the rifling of the barrel spun the shell as it was fired, so this was as precise as the clockwork in the shell allowed. Apparently, they shot down a lot of planes with that thing.
patkai 7y ago
I just read von Neumann's biography recently. He wanted to call the ENIAC the MANIAC - because of its unreliability - but his colleagues refused.
- segfaultbuserr 7y ago
  The name "MANIAC" (Mathematical Analyzer, Numerical Integrator, and Computer or Mathematical Analyzer, Numerator, Integrator, and Computer, https://en.wikipedia.org/wiki/MANIAC_I https://en.wikipedia.org/wiki/MANIAC_I) was eventually picked up by physicist Nicholas Metropolis to name a computer designed under his leadership, as an attempt to ridicule and stop the rash of silly acronyms for machine names, such as ENIAC, EDVAC, UNIVAC, etc.
mistrial9 7y ago
a programmer from Huntsville, Alabama started in 1963, and later worked on Burroughs equipment, and much later on MP/M, then Apple. Quite a clever fellow, many great stories.. hardware would certainly be down from time-to-time.

See also this work-in-progress ENIAC simulator: https://www.cs.drexel.edu/~bls96/eniac/ https://www.cs.drexel.edu/~bls96/eniac/

segfaultbuserr 7y ago
An interesting fact of ENIAC is, although it was originally programmed by plugboards in 1946, it was soon retrofitted to a stored-program computer in 1948 to simplify programming, using its spare function table units as ROM, and its extra accumulators as a program counter and a pointer. I wonder if there's any project to recreate an ENIAC simulation in stored-program mode.
- hcs 7y ago
  For anyone interested in this period, there's a book on the stored-program ENIAC: http://eniacinaction.com/ http://eniacinaction.com/

andrewstuart 7y ago

The thing that people might find hard to understand these days is that computers - particularly mainframe or minicomputers - were really unreliable. The hardware was often/always custom built and it would often just stop and the manufacturer had to come in to work out what was wrong, and fix it which typically involved replacing boards until the problem went away. I should note that I'm basing this experience of being involved with company in the late 1980's - not the 1940's which is the topic of this post. Although I can imagine that back then the machines would only run for a matter of hours at best before breaking down and needing debugging. It was the same with networking which was particularly unreliable when it ran over coaxial cables like RG58 which had an array of problems that would lead to the whole company network going down and taking all the connected PCs with it. Modern computing is incredibly reliable.

rootbear 7y ago
The early, first generation tube-based computers had tube failures more or less daily. Higher reliability tubes specifically intended for computers were eventually introduced. One trick was to run the tube filaments "derated", or under the rated voltage. The tubes worked fine as logic elements at the lower voltage although that probably messed up their normal response curves. When I saw the Colossus rebuild at Bletchley Park, I asked about tube failure and they confirmed that they run the tubes (or valves, as they call them) on the Colossus at derated voltage, greatly reducing the failure rate.
AnimalMuppet 7y ago
My mother was a programmer in the 1950s. Someone came in early every morning and ran memory tests. If a tray of memory failed, they replaced it so that the computer could run while a tech debugged the failing tray. (A tray was 100 words by 36 bits of tube memory.)
- dboreham 7y ago
  Same. Except my mother talks about replacing Valves (Vacuum Tubes).
  - hedora 7y ago
    When I visited the USS Hornet museum (WWII aircraft carrier docked in Oakland), our tour guide was the guy that used to replace vacuum tubes during combat. The targeting computer was analog, and controlled a very large anti aircraft gun using radar to to automatically track targets and compute parabolas. The gunner sat in a little control seat on the turret. When a tube blew, the whole turret would start oscillating violently. The job of our guide was to pull refrigerator-sized banks of vacuum tubes out of the wall, replace all the ones that looked dim, slam it shut, and move from bank to bank until it stopped trying to shake the poor gunner out of his seat. The shells had a timer inside them, and the people loading it had to set the delay between launch and detonation based on the time of flight the computer reported. The timer was actuated when the rifling of the barrel spun the shell as it was fired, so this was as precise as the clockwork in the shell allowed. Apparently, they shot down a lot of planes with that thing.

patkai 7y ago

I just read von Neumann's biography recently. He wanted to call the ENIAC the MANIAC - because of its unreliability - but his colleagues refused.

segfaultbuserr 7y ago
The name "MANIAC" (Mathematical Analyzer, Numerical Integrator, and Computer or Mathematical Analyzer, Numerator, Integrator, and Computer, https://en.wikipedia.org/wiki/MANIAC_I https://en.wikipedia.org/wiki/MANIAC_I) was eventually picked up by physicist Nicholas Metropolis to name a computer designed under his leadership, as an attempt to ridicule and stop the rash of silly acronyms for machine names, such as ENIAC, EDVAC, UNIVAC, etc.

mistrial9 7y ago

a programmer from Huntsville, Alabama started in 1963, and later worked on Burroughs equipment, and much later on MP/M, then Apple. Quite a clever fellow, many great stories.. hardware would certainly be down from time-to-time.