[Info-vax] OT: news from the trenches (re: Solaris)

[lists at openmailbox.org]

On Thu, 12 Mar 2015 23:47:33 +0000 (UTC)
glen herrmannsfeldt via Info-vax <info-vax at rbnsn.com> wrote:

> lists at openmailbox.org wrote:
> > On Thu, 12 Mar 2015 15:47:18 -0400
> > Stephen Hoffman via Info-vax <info-vax at rbnsn.com> wrote:
>  
> >> IBM has a very long history of emulating previous generations
>  
> > n the mainframe nothing has been emulated. Of course they pioneered
> > virtualization but the whole point of S/360 was one architecture
> > implemented on machines from large to extra large. You're suggesting
> > something that is completely infeasible, has never been done once in
> > over 50 years of production and you're suggesting it's a foregone
> > conclusion. That is just unsupportable and wrong.
> 
> Most models of S/360 also supported one or two previous generation
> machines, usually partially with special microcode and partially
> with software emulation. That allowed them to sell one to someone
> running an older machine as they slowly migrated up to S/360.

Well, a lot has been cut out from what I wrote and what you wrote just now
is not a refutation of any of that. Seeing your posts over the years I know
you have a good memory and like to mention a lot of neat facts so I don't
believe that was your intention anyway.

This is what I said that you didn't quote:

> > All the software ever written for the IBM mainframe depends on that
> > specific architecture and ISA. From 1964 until today the OS has never
> > been ported to another platform and it won't ever be. To get off the
> > box you have to emulate the hardware. The OS is too big and too
> > complicated and most of all too closely coupled to the hardware (which
> > is why it works so well) to ever be ported.

Your examples were of S/360 emulating a machine from a prior line of
computers. I already said that was what had to be done. But that wasn't the
central issue anwyay.

The whole discussion started with Hoffman's argument against what I had
written about my surprise at some of IBM's decisions lately and his claims
that:

> IBM is not going to reacquire the fabs, and they're not going to get 
> back into either the x86 or the fab business, and it would not surprise 
> me to see IBM eventually migrate to commodity x86-64 processors even on 
> their mainframes, assuming they don't spin off the z business. 

to which I replied there was no way to port the OS to different hardware. I
have already said that there were/are several hardware emulators before
anybody in this thread mentioned it.

But none of those emulators are remotely reasonable substitutes for a
mainframe, as anyone who has any understanding of what a mainframe is would
already know. They are certainly good enough for a couple of guys to
develop real software on. They are not capable of replacing a mainframe in
any aspect. You don't buy a mainframe to host a small development
group. You buy a mainframe to run a Fortune 500 company one.

Hoffman is conflating porting and emulation and speculating on things in
far away lands without any basis in reality. The more I read what he writes
the more I think there's a frustrated cost accountant screaming to come out
of the closet. Not every technical decision ought to be made by MBAs.
Sometimes there are technical reasons for doing things or not that
beancounters can't understand.

The mainframe is not just a CPU. It's a set of hardware and software that
has been designed and refined for a half century of production in the
biggest companies and governments in the world. Everything works together
symbiotically. The OS runs pretty nicely on Hercules but on the best Intel
hardware ever made or that ever will be made you could never run the
production workloads being run today. The I/O channels and RAS features
just aren't there, and Intel doesn't scale up. Mainframes don't scale out.
It's apples and rotten eggs.

The mainframe today is about retaining huge investments in code and to some
lesser degree people. You can't port z/OS to any other platform and you
can't port any of the vendor system software and also not a good portion of
the vendor application software. This is a closely coupled hardware and OS.

To paraphrase Hoffman, "z/OS isn't OpenVMS." VMS was ported twice already.
OS/360 and up have never been ported and they never will be ported. And not
only that, the machine emulation will never be good enough to run today's
production workloads on any other single box.

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