NIOS II Multi-Processor System's On-chip Memory

You wrote "all the processors are executing a same set of instructions simultaneously", by it I assume you mean the program, therefore all cores run the same program.

That also implies the same variables.

This is called Symmetrical Multi-processing (SMP) vs. each core running its own program (AMP: Asymmetrical Multi-Processing).

As they run the same program and share the same data, the program itself must have provision to use the core ID (or number) to select core-specific operations / memory accesses.

In your specific requirement about splitting the array, use the core ID# as an offset:

1 - Declare your array as a 1024 one, e.g. int Array[1024];

2 - The slave cores (#1->#4) access their area using this point:

MyPtr = &Array[(CoreID-1)*256];

Same program, same array, but different accesses by the individual cores

If your application needs synchronization, messages, queues, parallel processing, shared resources access, etc. you should seriously look at using a SMP RTOS.

Regards