Which Dec Emulation is the MOST useful and Versatile?

[Jon Elson]

On 10/29/2017 07:42 AM, Paul Koning via cctalk wrote:
>> On Oct 28, 2017, at 10:09 PM, Eric Smith via cctech <cctech at classiccmp.org> wrote:
>>
>> IBM invented computer emulation and introduced it with System/360 in 1964.
>> They defined it as using special-purpose hardware and/or microcode on a
>> computer to simulate a different computer.
> That's certainly a successful early commercial implementation of emulation, done using a particular implementation approach.  At least for some of the emulator features -- I believe you're talking about the 1401 emulator.  IBM didn't use that all the time; the emulator feature in the 360 model 44, to emlulate the missing instructions, uses standard 360 code.
Except for certain machines (360/44, 360/91-95 series, model 
195) all other 360's were also emulated by microcode.
there really was no difference in running 360 code or 1401 
code on a 360 system, they were both done by microcode 
emulation.

The 360/44 had no control store, so any emulation/simulation 
had to be done by a program written in 360 instructions.
The 360/44 was a hardwired 360.  Note that while the 360 was 
a 32-bit instruction set, the 360/30 had only an 8-bit data 
path, and the 360/40 had only a 16-bit data path.
> It's not clear if that IBM product amounts to inventing emulation.  It seems likely there are earlier ones, possibly not with that particular choice of implementation techniques.
>
>
>
Yes, there were others.  Burroughs and Univac also used 
microcode at about the same time.  I'm not sure the original 
DEC PDP-10 (KA-10) used microcode, but the KI-10 did.

Jon