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Re: [Qemu-devel] QEMU WIN32 Porting Installing W2K

From: J. Mayer
Subject: Re: [Qemu-devel] QEMU WIN32 Porting Installing W2K
Date: Thu, 16 Dec 2004 16:57:24 +0100

On Thu, 2004-12-16 at 04:49, Karl Magdsick wrote:
> > > 3.    Is there a way to emulate an AS 400 System using
> > > QEMU or other software?
> > 
> > what is AS 400?
> AS/400 is an IBM operating system for mid-range servers that runs on
> POWER chips. 

AS/400 run on regular RS64. I don't know much about RS64 but it seems to
be a regular 64 bits PPC with multithread feature (ie like
hyperthreading) and hypervisor capabilities.

> I believe the 604e and similar chips do not implement some of the
> functions required for AS/400.  I'm not sure about G3s, but I doubt
> it.  I believe QEMU emulates something G3-ish, so I don't think AS/400
> will run on the QEMU-emulated PPC CPU.  However, I could very well be
> wrong.

One thing is POWER/RS64 are 64 bits CPU while Qemu-PPC emulates only 32
bits CPU for now.

> I just did a quick search, and didn't find anything useful about
> AS/400.  IBM has something called OS/400 (now called i5/OS), but that
> looks like something in the OS/370, OS/390 family.  I don't think
> AS/400 is in the OS/370 family, but I could be wrong.  AS/400 may have
> been phased out.

AS400 is not in the mainframe (ie OS/370 & 390) family and the CPU and
design are very different.
One problem is to get detailed informations about the hardware in order
to emulate it.
In a other hand, the virtual devices seem not to be so complicated.

> It would be really cool if eventually QEMU could emulate IBM POWER
> based servers well enough to run IBM's hypervisor.  The hypervisor
> virtualizes the hardware for the operating system(s) proper and
> provides resource partitioning.

I don't think the hypervisor feature is really hard to emulate. It's a
kind of very simple MMU feature with OS partitions defined by their
physical memory address base and size. But you'll need a lot of memory
to be able to launch many OSes.
A first point would be to launch one OS using OF, RTAS and hypervisor
virtual devices but with only one LPAR.

IMHO, the main problem is then to emulate 64 bits PPC/Power and make
qemu safe and running well on 64 bits host then (maybe) emulate 64 bits
targets on 32 bits host, but this will be very slow if it ever work...
J. Mayer <address@hidden>
Never organized

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