Which Dec Emulation is the MOST useful and Versatile?

[Eric Smith]

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.

Anything you run on your x86 (or ARM, MIPS, SPARC, Alpha, etc) does not
meet that definition, and is a simulator, since those processors have only
general-purpose hardware and microcode.

Lots of people have other definitions of "emulator" which they've just
pulled out of their a**, but since the System/360 architects invented it, I
see no good reason to prefer anyone else's definition.