Talk:Von Neumann architecture

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Removing redundant diagram[edit]

There are two diagrams, both with the caption "Von Neumann architecture scheme", that are almost identical. The only real difference, other than color, is that the input and output devices are shown connecting directly to the accumulator in the arithmetic logic unit in the second example, rather than to the unit as a whole. I believe that is less accurate. Hence, I am removing the reference to the second diagram. - AlanUS (talk) 20:53, 7 January 2016 (UTC)

Agreed. Andy Dingley (talk) 22:44, 7 January 2016 (UTC)
The one you left in was a newer addition to the page; you removed the older one. I consider the one you left there to be better than the one you removed, so I think you did the right thing here. Guy Harris (talk) 22:55, 7 January 2016 (UTC)

an original work of Von Neumann[edit]

IMHO the book or article, where Von Neumann architecture was introduced should be mentioned (with a link, if possible) —Preceding unsigned comment added by (talkcontribs) 03:08, 18 April 2005

There it is... You could have done it yourself, it only took two quick Google searches (one on "von neumann architecture eniac" to find the title and one on the title to find a PDF of the paper itself). -- RTC 21:54, 18 Apr 2005 (UTC)

Earliest dates for stored program computers[edit]

If anyone has more information for the dates about the earlies stored program computers, please include it. --Bubba73 05:49, 4 Jun 2005 (UTC)

Harvard architecture "more modern" than von Neumann architecture?[edit]

The machine that inspired the use of the term "Harvard architecture", the Harvard Mark I, first ran in 1944; the First Draft of a Report on the EDVAC by von Neumann, which inspired the use of the term "von Neumann architecture", was published in 1945.

In what fashion is the Harvard architecture "more modern than" the von Neumann architecture? Processors in which there are separate level 1 instruction and data caches, and separate data and address lines to those caches, are a relatively modern development, but that's, at best, a modified Harvard architecture, and arguably is better called a "split cache architecture", with the only difference between it and a von Neumann architecture being, at most, a requirement to flush the instruction cache following a store operation that modifies an in-memory instruction (and split-cache x86 processors, due to backwards-compatibility requirements, don't even need that). Guy Harris (talk) 08:03, 9 November 2014 (UTC)

And Turing's report on the Automatic Computing Engine also dates to 1945. Guy Harris (talk) 09:38, 9 November 2014 (UTC)

Was ENIAC a von Neumann-architecture computer?[edit]

At least two IP addresses have added ENIAC to the list of von Neumann architecture computers. According to the article for ENIAC, it was originally programmed with switches and cables (not von Neumann. Then the ability to put programs into the function table, which was a set of switches (read-only by the machine) was added; that would make it a Harvard architecture machine, not a von Neumann architecture machine. That was described in A Logical Coding System Applied to the ENIAC (Electronic Numerical Integrator and Computer) from 1948. Then a core memory was added in 1953; I don't know whether words from that memory could control the operation of the machine or not, but, even if it did, that wouldn't make ENIAC a von Neumann architecture machine until 1953. Guy Harris (talk) 05:45, 10 April 2015 (UTC)

I believe that you are correct. The 1945 ENIAC wasn't a stored program computer of any kind.; it was programmed with knobs and plugboards.[1][2] The 1948 ENIAC was a stored-program computer using read-only memory -- a Harvard architecture.[3]
(Unrelated but interesting:[4][5][6])
As for the 1953 ENIAC, does anyone have access to A static magnetic memory system for the ENIAC (ACM '52 Proceedings of the 1952 ACM national meeting (Pittsburgh) Pages 213-222 ACM New York, NY, USA ©1952 doi 10.1145/609784.609813)?[7] --Guy Macon (talk) 10:48, 10 April 2015 (UTC)
Yes, I just bought it. The article says "At present the ENIAC has only 20 words of internal memory, in the form of electronic accumulators. This small memory capacity limits the size of the problem that can be programmed without repeated reference to the external punched-card memory." (which is in the summary that you can get for free), which seems to suggest that it's additional data memory. In section IV "The Memory System for the ENIAC" it says that one of the requirements is "that the control signals used in the memory be derived from the standard control pulses in the ENIAC", which suggests that it didn't itself generate control signals, i.e. it couldn't contain code.
Article such as this one from 1961 seem don't speak of the core memory as a particularly significant change, unlike the description of the function table read-only code memory:
Programming new problems meant weeks of checking and set-up time, for the ENIAC was designed as a general-purpose computer with logical changes provided by plug-and-socket connections between accumulators, function tables, and input-output units. However, the ENIAC's primary area of application was ballistics--mainly the differential equations of motion.
In view of this, the ENIAC was converted into an internally stored fixed-program computer when the late Dr. John von Neumann of the Institute for Advanced Study at Princeton suggested that code selection be made by means of switches so that cable connections could remain fixed for most standard trajectory problems. After that, considerable time was saved when problems were changed.
The ENIAC performed arithmetic and transfer operations simultaneously. Concurrent operation caused programming difficulties. A converter code was devised to enable serial operation. Each function table, as a result of these changes, became available for the storage of 600 two-decimal digit instructions.
Those revolutionary modifications, installed early in 1948, converted ENIAC into a serial instruction execution machine with internal parallel transfer of decimal information. The original pluggable connections came to be regarded as permanent wiring by most BRL personnel.
so I suspect the machine remained a Harvard architecture machine after the core memory was added. Guy Harris (talk) 18:29, 10 April 2015 (UTC)