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From: gcwilliams@watdragon.waterloo.edu (Graeme Williams)
Newsgroups: comp.arch
Subject: Re: EFLOP architectures: when and for how much?
Summary: Fundamental restrictions imposed by physics
Message-ID: <1990Oct26.191032.9099@watdragon.waterloo.edu>
Date: 26 Oct 90 19:10:32 GMT
References: <1990Oct2.190020.15214@mdbs.uucp>
Sender: gcwilliams@watdragon.waterloo.edu
Organization: University of Waterloo
Lines: 34

In article <1990Oct2.190020.15214@mdbs.uucp> zed@mdbs.uucp (Bill Smith) writes:
>When was (or will) machines with the following performance be available?  
>
>					Date:			Cost:
>Mega FLOP  --  10^6  (MFLOP)    
>Giga FLOP  --  10^9  (GFLOP)
>Tera FLOP  --  10^12 (TFLOP)
>Peta FLOP  --  10^15 (PFLOP)
>Exa  FLOP  --  10^18 (EFLOP)

The higher two of these are probably unattainable in the forseeable
future - except perhaps for very large numbers of processors in parallel.

For *SINGLE* processors there is a fundamental restriction on the number
of operations that can be performed.

Namely :
An instruction cannot be executed in a time shorter than the time
it takes for a light beam to traverse the processing device.

Thus if a single processor were to be capable of executing 10^18
instructions per second - the physical size of the processor would
have to be smaller than (3*10^8)/10^18 metres i.e. 0.3 nanometres.

Unfortunately 0.3 nanometres is the same order of size as a single
molecule - so either the processor is *EXTREMELY SIMPLE* :-) ,or it's
not made of molecules! In short 10^18 operations/sec will probably
be forever impossible for a single processor, indeed 10^15 probably
is too.

Anyone for engineering a CPU out of a tiny piece of neutron star ???

Graeme Williams
gcwilliams@watdragon.waterloo.edu