RE: LPAR, Upgrades, New Hardware

>From: Joe Pluta [mailto:joepluta@xxxxxxxxxxxxxxxxx] 
>No, there's a third option, the concept of writing to a virtual machine
>layer.  If your operating system talks to a virtualized hardware layer
>rather than directly to the hardware, then all you need to rewrite is the
>VM.  This is the concept that has made Java so successful, and is the same
>thing that the AS/400 uses, as IBM itself says:

Yes and no (gee, what a shock, Joe and I don't agree <G>). What you say is
very true of application programs, and it's what allows my System 38 app to
run on the newest hardware running V5R2 w/o ever recompiling. However, keep
in mind we're talking about the OS here, not an application. I have no doubt
there are portions of V5R2 that would run on a B10 thanks to TIMI, but only
portions. You make a comparison of OS/400 to a Java application. I'd modify
that a little. OS/400 is a bizarre hybrid of a java application (which can
be ported) and the JVM itself (which can't). 

As you well know, what makes Java portable isn't that it's this great and
wonderful language that somehow succeeded where Pascal, Cobol, C, C++, etc.
failed in cross-platform ideals. But rather Java's success is based on the
fact that Sun has kept the proprietary Java "standard" standard! They've
said "if you're going to call it Java it must look like this!" and lots of
people have implemented this JVM standard across lots of platforms. 

If OS/400 is part app and part JVM you can't expect to pick it up and drop
it on another hardware platform any more than I can expect to pickup the
Solaris JVM and run it on zOS.

-Walden

------------
Walden H Leverich III
President
Tech Software
(516) 627-3800 x11
(208) 692-3308 eFax
WaldenL@xxxxxxxxxxxxxxx
http://www.TechSoftInc.com 

Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)
 

-----Original Message-----
From: Joe Pluta [mailto:joepluta@xxxxxxxxxxxxxxxxx] 
Sent: Tuesday, May 13, 2003 12:15 PM
To: Midrange Systems Technical Discussion
Subject: LPAR, Upgrades, New Hardware


> From: Larry Bolhuis
>
>   As you no doubt know there are only two ways for an 'old' OS to run on
> a 'new' piece of hardware. a) the hardware emulates older hardware
(...)
> or the software gets a boost to support the new hardware.

No, there's a third option, the concept of writing to a virtual machine
layer.  If your operating system talks to a virtualized hardware layer
rather than directly to the hardware, then all you need to rewrite is the
VM.  This is the concept that has made Java so successful, and is the same
thing that the AS/400 uses, as IBM itself says:

"Both Java and AS/400 are based on the same fundamental principle. The
source code is converted to an intermediate form that runs on a virtual
machine so that even if the underlying hardware machine changes
significantly (in the AS/400 case), or is purposely abstract so that it can
be any underlying machine architecture (Java), the source code need never be
recompiled to run on this new machine."

The page this came from is actually pretty interesting reading:

http://www-1.ibm.com/servers/eserver/iseries/whpapr/dev_toolkit_java.html


>From what I understand, the TIMI is the "Technology Independent Machine
Interface", which should not change from hardware to hardware, and the SLIC
is the part that changes.  By adapting the SLIC to the new hardware, you
should theoretically be able to support previous releases with no problems.

Joe

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