If I understand correctly modern computers are modeled after the Von Neumann architecture. I have sometimes seen reference to alternatives, but haven t really seen any very good descriptions of how non-Von Neumann architectures would be organised and function.
Does anyone have any examples? What are the advantages/disadvantages of alternative computer organization?
I believe the most common one would be the Harvard architecture or the Modified Harvard architecture which is used in a lot of ARM based chips. I am sure there are many differences, but here is one that stands out
In a computer using the Harvard architecture, the CPU can both read an instruction and perform a data memory access at the same time, even without a cache.
Examples of non von Neumann machines are the dataflow machines and the reduction machines. In both of these cases there is a high degree of parallelism, and instead of variables there are immutable bindings between names and constant values. non von Neumann is usually reserved for machines that represent a radical departure from the von Neumann model, and is therefore not normally applied to multiprocessor or multicomputer architectures, which effectively offer a set of cooperating von Neumann machines.
Cellular automata - this predated neural network, but the ideas are very similar.
http://en.wikipedia.org/wiki/Cellular_automaton
Neural networks can be viewed as a form of cellular automata, or a distinct non-von Neuman architecture of their own.
Quantum computers are also another example. They differ from other computers, mainly because of the order of time needed for a problem to be solved on them. Classical computers can be modeled using a Turing machine whether von Neuman or Harvard. They have their own model called a Quantum Turing Machine.
data flow computers and reduction computers are the example of non von neumann arhchitecture.
Another example: The machines that are not problem independent (the case of most of the machines today).
An obviously Example is the Enigma-Machine. Used by German Army in the Second World War: It can solve just one problem: The encription of Communications!
In v. Neumann Architectures the Machines should be capable to solve any possible problem. The only limitation that time was actually the technologies used to build computers :P
What about Analog Computers? I guess they use different architecture.
The Brain could be considered a non-von neumann architecture computer. IBM is currently working on a non-von neumann solution. HP labs "The Machine" may also be non von-neumann.
PIC microcontrollers use the Harvard architecture. See www.microchip.com or https://en.wikipedia.org/wiki/PIC_microcontroller. These are very cheap controllers that can be programmed to control different devices, like turning on lights or starting a motor. The fun part from programming point of view is that the program code is in memory and all variables are kept in registers.
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