An effective way of simulating Nios II designs (Modelsim ASE)

I'm currently using Nios II Modelsim ASE for simulating my Nios II based designs, with my C language code developed in "Nios II SBT for Eclipse" environment.

Now I can watch results of my designs only through Modelsim ASE RTL waveforms and printf calls on a simulated JTAG UART, but I have no mean to access to variables, set breakpoints, or doing any other thing more effective to debug my code.

Does anyone know a better way to simulate Nios II based designs which doesn't require to own a development board? (actually, I've got a DE1, but I need to explore purely software debugging solutions because I have to show how to use Altera tools to a class of students who don't have boards).

Thank you in advance for any help you can give me.

Regards,

Lorenzo