29 Oct
2017
29 Oct
'17
1:43 p.m.
On 10/29/2017 07:42 AM, Paul Koning via cctalk wrote:
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.
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. 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