PASE Brings AIX Applications to the AS/400

I remember someone asking about this a while ago.  Sounds cool
Just need to find some documentation.

Bryan Dietz

(from the mmu)

PASE Brings AIX Applications to the AS/400
=======================================



The star of this week's PartnerWorld 2000 trade show in San
Diego, at least as far as AS/400 customers are concerned,
is a new option for the AS/400 called PASE. That acronym
stands for Portable Applications Solutions Environment (not
Private Address Space Environment as has been reported by
us and our competition in the AS/400 news-gathering
business). PASE is a UNIX runtime environment that is an add-
on feature for OS/400. It is something that the AS/400 has
needed for years: an easier way to get UNIX applications up
and running natively on the AS/400. IBM gave me a rundown
on PASE last week so I could tell you about it concurrent
with the announcement.
     PASE is possible for a number of different reasons;
not the least of which is the fact that since the Apache
generation was announced in September 1997, AS/400 and RS/
6000 servers have used essentially the same hardware:
processors, memory cards, system buses, etc. The basic
differences between an AS/400 and an RS/6000 symmetric
multiprocessing server are that the AS/400 and RS/6000
applications sometimes use different instructions that are
embedded into the 64-bit PowerPC chips (Apache, Northstar,
Pulsar) and the RS/6000 has a slightly different I/O setup
(high-end AS/400s use proprietary SPD peripheral
connections; the RS/6000 uses PCI technology, like PC and
UNIX servers).
     Over the past year or so, PASE has moved from a toy to
a strategic porting environment. Early last year, I heard a
story about how the techies at Rochester had taken an AIX
implementation of the Asteroids video game and ported it to
the AS/400. Exactly how they did this was unclear to me at
the time, and I didn't give a lot of thought to it, because
these kinds of research projects are always going on behind
the scenes. For instance, IBM has been similarly playing
around with Non-Uniform Memory Access (NUMA) clustering and
Very Long Instruction Word (VLIW) programming techniques
for AS/400s since the early 1990s, and while that research
has led to improvements in the AS/400, it has not (yet)
resulted in NUMA or VLIW products. For those of you who
remember IBM history, in the mid-1990s, in the wake of the
PowerPC alliance that it created with chip maker Motorola
and PC maker Apple, IBM had a plan that involved creating a
new operating system kernel called WorkPlace OS, which
would run on PowerPC chips and then allow a single machine
to support OS/400, AIX, MacOS, Windows NT, and any other
operating system that supported the PowerPC architecture.
This is another research project that never came to pass--
OS/400 and AIX have very unique operating system kernels and
Windows NT has not been supported on PowerPC iron for years-
-although I would guess that IBM has used the lessons it
learned with WorkPlace OS to create PASE. Anyway, being a
fan of Asteroids myself--my high score since I got the
Windows version is a pathetic 36,200 because I play while
talking to people and don't multitask all that well--I can
understand why the Rochester developers wanted to port it
to the AS/400: to see if they could do it. Apparently, since
I first heard about Asteroids for AS/400, AS/400 Division
General Manager Tom Jarosh has pushed developers to expand
the minimal UNIX runtime environment that was running
Asteroids to the point where it can be used to support full-
blooded AIX applications natively on AS/400 iron.
     Early rumors about PASE said it was a runtime
environment but required recompilation of UNIX applications
to work. This latter bit was not correct. PASE is indeed a
runtime environment--for AIX binary applications,
specifically. So far, it is unclear what limitations there
are among those binaries, but it is clear that PASE does
not require recompilation of those binaries from source code.
 Because the Apaches and Northstars have both the AS/400 and
RS/6000 instruction sets in them, AIX applications, when
properly surrounded with a minimal AIX environment to
support AIX binaries and libraries, can reach down into the
AS/400 iron and run. The AIX kernel has not been ported to
OS/400, so this is not a case of IBM running both AIX and
OS/400 on a single box. PASE does not require an OS/400
logical partition to isolate the PASE environment from
other OS/400 workloads. OS/400 remains firmly in control of
AIX applications, and these AIX applications are running,
at least during preliminary tests, at native speeds compared
to RS/6000 implementations of the same applications.

     The first pass of PASE includes over 900 AIX
application programming interfaces that AIX applications
typically talk to get access to Apache or Northstar
hardware. These APIs are what comprise the minimal AIX
runtime environment, and the whole shebang is woven into OS/
400's Systems Licensed Internal Code (SLIC). This runtime
environment gives AIX binaries the things they expect to
see--such as support for the ASCII character set, 32-bit
pointers, and so forth-and, for all intents and purposes,
looks like AIX, as far as the application is concerned.
With PASE, application developers don't have to go through
the process of examining their UNIX C code and comparing C
features supported in AIX with those supported in the AS/
400's ILE C compilers. They also don't have to worry so
much about whether or not OS/400 has the UNIX APIs that
other UNIX environments have; the AS/400 has long since
offered support for all but the supercomputing APIs in the
so-called SPEC 1170 group of popular UNIX APIs; OS/400 also
supports the open systems POSIX standard, which describes
file types among other things. These UNIX features help
make it easier for UNIX developers to get their code running
under OS/400. But moving from UNIX to OS/400 was often no
easier, and sometimes harder, than moving from one UNIX
variant to another. (Just because an API exists, doesn't
mean it works well, and performance differences in APIs is
one of the things that drive application software vendors
crazy. The APIs have to work well for these vendors to
announce a port to a new platform like the AS/400.)

     PASE is a much simpler approach: Load the AIX
application in the AS/400's QopenSys file system within the
Integrated File System (IFS) and invoke it from an ILE API.
If the application uses only those 900+ AIX APIs supported
by PASE, it loads into a private address space in the AS/
400's memory and runs. The AIX applications within PASE can
access AS/400 databases just like other AS/400 applications,
 and they can call ILE RPG, C, and Java programs written
specifically for the OS/400 environment, too. IBM says that,
 as it evolves the PASE software, it will add more AIX APIs,
which should broaden the number of AIX applications that
can be run on the AS/400. It is also providing Business
Partners with all kinds of tools and support to help them
figure out if their AIX applications are a good fit for
PASE. We'll have more on PASE next week as we learn more
about what it can and cannot do. To get more information on
PASE, you can jump over to a story written by IBM, which
will be available late Monday afternoon EST under the AS/
400 Network Expert Web site at
http://www.midrangecomputing.com/ane/. IBM will also have a special
Web site for PASE available on January 24 at
http://www.as400.ibm.com/developer/factory/pase.





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