It's challenge in other places as well. Consider IBM i itself. At i 5.4(.5) the LIC had to support Power6 and Power5, the i8xx family and its SStar processors, AND the 270/820 family with its iStar processors! So when you compiled a program for example it generated code that could execute on any of those processors. Thus as it works out the only time you could FULLY exploit the capability of a processor was in the FINAL release that supported that processor! Of course that processor is clearly old at that point!

So i 5.4 was the 'best' at utilizing an iStar, i 6.1 for SStar, i 7.1 for POWER5.

Fortunately this was observed by IBM and they decided it was not optimal. Beginning with i 7.1 they compile to the processor of the machine you are compiling on. Thus if you're on a POWER7 and i 7.1 it knows to use POWER7 code. If that program is moved to POWER8 it will still run but as a POWER7 program. If it's moved to a POWER6 or POWER5 machine it will be re-encapsulated to enable it to run on the older processor.

- Larry "DrFranken" Bolhuis - Personal Development IBM i timeshare service. - Commercial IBM i Cloud Hosting.

On 12/3/2015 9:59 AM, rob@xxxxxxxxx wrote:

I'm really torn on whether or not support for X-2 is a good thing.

(Numbers below are not actual [especially java versions] and are only for
example purposes.)

Let's say that IBM has a program called WONDERFUL. Let's say WONDERFUL
v1.0 starts on V5R3 and requires Java 3. Let's say that J3 was supported
on both V5R4 and 6.1 (probably isn't, again the java versions are only
examples). So now you can continue to run WONDERFUL v1.0 on both V5R4 and
6.1. Let's say that Java 1 was dropped with V5R4 and Java 4 was added.
Let's say that Java 2 was dropped with 6.1 and Java 5 was added. Now
let's say that 7.1 comes out, drops Java 3 support and adds Java 6. IBM
comes out with WONDERFUL v2.0. In order to support X-2 they cripple by
having it run Java 4 so WONDERFUL v2.0 can run on V5R4 thru 7.1. This
will allow those on V5R4 to upgrade from WONDERFUL 1.0 to 2.0 and then
upgrade their OS from V5R4 straight to 7.1. Now let's say that IBM i 7.2
comes out, drops Java 4 and adds Java 7. So IBM comes out with WONDERFUL
3.0. In order to support X-2 they cripple this by only supporting Java 5.
So those running 6.1 can upgrade to WONDERFUL 3.0 and then upgrade from
6.1 to 7.2.

Personally I find upgrading WONDERFUL to be much more disruptive than
upgrading IBM i. I don't often do 'skips'. I would rather they take
advantage of a higher version of Java and whatnot.
Especially when IBM may not have the latest version of WONDERFUL ready at
IBM i release time.

I guess if IBM just had the latest version of WONDERFUL available a
quarter of a year before IBM i release date I wouldn't mind so much.

Rob Berendt

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