Emulator vs. Simulator, was Re: Double HIgh Resolution Question

[mjmahon@aol.com (Michael J. Mahon)]

Eric Smith wrote:

>In 1964, IBM defined "emulator" as regarding computers to be
>simulation based on dedicated hardware or microcode.  Presumably you're
>not developing hardware or microcode, so what you're working on is a
>simulator.  Some people object to the use of the word simulator because
>they think somehow that a simulator is less accurate than an emulator,
>but there is nothing inherent in the definition of simulator that
>requires or even implies this.
>
>The first computer emulators were the options for the IBM 360/30, /40,
>/50, and /65 which were implemented in a combination of hardware and
>microcode, and allowed the user to run programs written for IBM's
>earlier families of computers such as the 1401, 1410, 7010, and 7090.
>Most later IBM mainframes dropped the emulator hardware and microcode,
>and used pure simulators instead.

I understand the point you are trying to make, and agree with your
facts.  I differ a bit on usage, however.  ;-)

Because the first IBM emulators were intended to run the software
of an older machine on their newer machines, and this was not
commonly done, the implicit definition of "emulator" became
associated with "what was accomplished" and not "how it was
accomplished".  It is in this sense that the term "emulator" is
most often used today.

Today "simulator" is usually reserved for a partial simulation of
a real machine (like a 747), or, more often in the computer
business, a "soft" implementation of a not-yet-existent machine.

This is reasonable, since "to emulate" is to imitate an existing
(usually good) example, in a non-computer context.  It is then
a straightforward extension to the computer context.

It is not the first time that the first to coin a usage did not have
the final say in what it conventionally "means", which is, after
all, what language is about.

-michael

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