Re: Question on TIMI implementation.

[Dave McKenzie <davemck@xxxxxxxxxxxxx>]

That IBM paragraph is somewhat misleading.  When it says "translated
into actual hardware instructions by the SLIC kernel prior to
execution", it doesn't mean *just* prior to execution (as in
Just-In-Time compilation).

The translation is a step in the compile process.  After the compile,
both the intermediate TIMI code and the PowerPC machine instructions are
stored in the program.  At execution time, the PowerPC instructions are
executed -- the TIMI code is ignored at execution time.

The TIMI code is only used if the program has to be re-translated from
TIMI to PowerPC instructions, such as when a program compiled on a
pre-Power6 machine is restored onto a Power6 machine.

--Dave

McKown, John wrote:
> I don't know if I understand the following paragraph that I got from
> IBM's web site:
>
> <quote>
>
> Traditional System i applications run under a model known as IBM
> Integrated Language Environment(r) (ILE). This model allows C/C++, RPG,
> CL and COBOL applications to easily call functions from, and share data
> with, each other through interaction that occurs at the TIMI level.
> Above the TIMI, all programs compile to an intermediate form that is
> automatically translated into actual hardware instructions by the SLIC
> kernel prior to execution. ILE applications are not interpreted.
>
> </quote>
>
> To me, the last sentence is saying that the program compiled to the
> TIMI. But when the program is loaded for execution, the TIMI
> instructions are transparently converted (compiled)  to pSeries
> instructions and then that temporary copy of the program is actually run
> "natively" (without using a emulator). As opposed to the program being
> loaded for execution and a TIMI emulator in "firmware" then running the
> program by reading each TIMI instruction and executing the necessary
> pSeries instructions.
>
> Hope my question makes sense.
>
> John McKown 
>
> Systems Engineer IV
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