On Tue, 12 Dec 2006 06:58:38 -0600, Chase, John <[EMAIL PROTECTED]> wrote:
>...
>Emulate [emulator]:
>
>3. Computers. a. to imitate (a particular computer system) by using a
>software system, often including a microprogram or another computer that
>enables it to do the same work, run the same programs, etc., as the
>first.
>b. to replace (software) with hardware to perform the same task.
>
>Simulator:
>
>2. a machine for simulating certain environmental and other conditions
>for purposes of training or experimentation: a flight simulator.
>
>Not a whole lot of difference there....
>...
Back in the olden days (like the late '60s) IBM had good samples of each,
and the destinction was very clear. S/360 customers had to run 1401
programs, and IBM provided the ability to do that on some S/360 models.
The Mod 30 had a 1401 emulator. You ran a configuration deck into the
system and the microcode allowed the hardware to execute 1401 code.
The Mod 40 (and probably higher models) had a 1401 simulator. You
executed the simulator (an s/360 program. I don't remember what operating
system) and it would read and process the the 1401 programs. I have no
idea haow this was accomplished. There very well may have been microcode
assists of some type.
Thos 2 samples both gloss over tons of details, but the difference is
clear. The emulator system executes the emulated system's instruction
set. The simulator executes its own "native" instruction set. (And in
both cases you may have under-the-covers microcode executing some
completely different microcode.)
Pat O'Keefe
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