OK - that makes sense now.

But you previously said that you were not doing it for an actual microcontroller;
you previously said that you were interested only in the simulation running on a PC - that was the bit that didn't make sense!


Of course the Keil C51 compiler does that!

But it is up to you the programmer to write a suitable program in the first place.

That means that you the programmer have to understand how the 8051 works. Once you understand how the 8051 works, then you can write programs to take advantage of that...

You probably now need to lay this project aside for a while and go back to basics with the 8051 architecture, and the basics of how to use the Keil tools.

For the 8051 basics, see: http://www.8052.com/faqs/120112
and: http://www.8052.com/tutorial
and: http://www.keil.com/books/
and, of course, the Data Sheet for the particular chip(s) that you will be using.

For getting started with Keil, see: http://www.keil.com/support/man/docs/gs/
and: http://www.keil.com/support/m..._hello.htm