Why does NIOS write redundant stuff to SDRAM?

[Altera_Forum]

Hi, 

 I have built a system with PCIe-NIOS-SDRAM, with the program being stored in a separate onchip memory. I am able to read and write data to SDRAM through PCIe, And also able to read and write from NIOS2, but I observe the following things; + When I use Printf statement in NIOS2IDE, I get the ascii code of printf written to SDRAM! This doesn't make any sense to me, I think its a debug feature, if so I would like to turn it off.  + If I don't use printf. still a few unintended bytes are written in the code space of SDRAM. But I don't want to leave any memory locations for program, thats why I have the on chip memory.  Please let me know how to solve the above issues. I can provide more information, please let me know..  Thanks, Ujjwal

[Altera_Forum]

It sounds like your BSP linker script is not set correctly to only use the onchip memory. Check it in the BSP editor.

[Altera_Forum]

Hi Ted, 

 Thanks for your reply.   Please find attached the contents of my linker script. Is it fine? Or should I change my .heap and .stack to onchip memory instead of SDRAM?  Ujjwal

[Altera_Forum]

The printf code almost certainly uses malloced memory - which is why you are seeing in in SDRAM. 

I would certainly try to get the stack in on-chip memory - and to use tightly coupled on-chip memory so you don't need to allocate resources to a data cache or large i-cache (you still need an i-cache for the boot code and JTAG debug - unless you are loading the code over PCIe).  If you do nee careful placement of code/data in memory blocks. I'd suggest writing your own linker script from scratch - start from the documentation rather than the default script!