RE: Re: MI emulator -- MI400

Firstly, the OS doesn't 'run' on MI - nothing 'runs' on MI. Remember MI is a 
language that ends up being compiled into PPC RISC instructions. The only thing 
really special about using MI is that you can use some of the core routines 
that all the other languages map to, via their own language constructs. For 
example, memset() in C/C++ is nothing more than a call to the same routine that 
CPYBWP maps to.

OS/400 is written in a number of high and low level languages, C++, MI, PL1, 
PLMI, Pascal, etc., and if you're on an older release you may even find some 
things that were done in Modular-2.

They all interface to the TIMI which can be thought of as the upper interface 
of the SLIC routines, these again are just PPC RISC instruction streams. For 
the high level ILE languages, the CUBE3 back-end compiler takes a intermediate 
representation (called w-code) and creates the program/module object full of 
PPC RISC instructions that interface with the TIMI.

To do what you ask, I think you'd really need;

(a) PPC emulator to run on Intel - kind of not doable unless you also want to 
write a thunking layer too. Also not doable as the iSeries version of the PPC 
is tainted with additional undocumented RISC instruction sets.
(b) To emulate the other completely undocumented IOP's used on the iSeries too.

The kind of effort to emulate the iSeries is not just simply writing a 'MI' 
emulator - you're effectively asking the same as;

Is it possible to write a CRAY-II emulator on Intel ?

Sure, you can try and you may get a certain percentage completed - but the 
nitty gritty machine 'idiosyncrasies' will very quickly make it a huge mountain 
of work.

Even the 'simple' emulators (PSOne & PS2, MAME, Vic20, BBC-B etc.) on Intel 
take a huge amount of work to get close to being 100% emulators.

--phil


> -----Original Message-----
> From: Olivier THEBAULT [mailto:mail@xxxxxxxxxxxxxxxxxxxx]
> Sent: Wednesday, October 08, 2003 4:22 PM
> To: MI Programming on the AS400 / iSeries
> Subject: [MI400] Re: MI emulator
> 
> 
> 
> OS/400 doesn't run on MI ?
> 
> ----- Original Message -----
> From: "Leif Svalgaard" <leif=vPETv0UHqg8@xxxxxxxxxxxxxxxx>
> Newsgroups: gmane.comp.lang.as400.mi
> Sent: Tuesday, October 07, 2003 11:10 PM
> Subject: Re: MI emulator
> 
> 
> > Olivier THEBAULT 
> <othebault=39ZsbGIQGT5GWvitb5QawA@xxxxxxxxxxxxxxxx> wrote
> in message
> > news:blv049$7ln$1=WnDAp88bSu0nT+UIioQ8UA@xxxxxxxxxxxxxxxx
> > > Is it possible to create a MI emulator on Intel processor ?
> > >
> >
> > yes, and not all that difficult. I guess that your real question is
> > if by having an MI-emulator one could run "normal" AS/400
> > programs on Intel. The answer to that is "no", because OS/400
> > is not written in MI and would have to be written for the Intel
> > processor. This is not easy because so much of OS/400 is
> > undocumented and also because OS/400 is so HUGE.
> >
> >
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