Which Dec Emulation is the MOST useful and Versatile?

Dave Wade dave.g4ugm at gmail.com
Mon Oct 30 09:58:55 CDT 2017



The folks who made ENIAC programable didn’t use the word “program” but they ran what we would now call programs. The fact that the word wasn’t used doesn’t mean the concept hadn’t already been invented. I did check and Turing didn’t use the term in his paper “On Computable Numbers” and whilst the work “emulate” is now associated with Universal Turing Machines I am inclined to agree that Turing probably didn’t see this as “Emulation” in the modern sense of the word, but to me, there seems to be little difference between a UTM and SIMH….


Returning to ENIAC if you read Mark Priestley & Thomas Haig’s paper




you can see they describe ENIAC in stored program mode as “a microcoded interpreter for a virtual von Neumann architecture machine” which seems to me to be equivalent to what IBM did, some years earlier. 

When I spoke to Mark Priestley after the talk..




he was quite clear that they configured ENIAC to emulate an EDVAC style machine and used the word “emulate” several times in the talk, so I would argue that the ENIAC pioneers invented the concept but did not name it as such…







From: Eric Smith [mailto:spacewar at gmail.com] 
Sent: 30 October 2017 11:18
To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>; Dave Wade <dave.g4ugm at gmail.com>
Subject: RE: Which Dec Emulation is the MOST useful and Versatile?


On Oct 29, 2017 09:54, "Dave Wade via cctalk" <cctalk at classiccmp.org <mailto:cctalk at classiccmp.org> > wrote:

I am not sure they invented computer emulation. I think that the concept
Emulation/Simulation is as old as, or perhaps even older than computing.
Whilst it was a pure concept Alan Turing's "Universal Turing Machine" was a
Turing machine that could emulate or simulate the behaviour of any arbitrary
Turing machine...


1. Did Turing use the word "emulate"? I honestly have no idea. My (possibly wrong) impression was that no published literature used the word emulate with that meaning (one computer emulating another) before the IBM papers.


2. What a UTM does is simulate another machine using only a general-purpose machine. In fact, the UTM is arguably the most general-purpose machine ever described. What IBM defined as emulation was use of extremely specialized hardware and/or microcode (specifically, not the machine's general-purpose microcode used for natively programming the host machine). If anyone else did _that_ in a product before IBM, I'm very interested.




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