> since i´m using the Large
> model (default xdata).

Thats the wrong way !

You must do the opposite, use Small model and place some variables into idata, pdata and xdata.

Only then you can see an effect on speeding up and size down the code.

But be aware, the default startup.a51 reserve only one byte as stack, which was insufficient in any case.
So at first you must change it. On my projects often a value of 16 bytes of stack was sufficient.

Furthermore you must tell the linker, that 256 bytes of RAM available.


Peter