NVRAM last sector, how implemented on 2/4MB flash

I have some issue with loosing whole nvram configuration at 9c9215 board. I suspect that problem is with flash size. I have a feeling that nvram is located at different addres according software configuration.
For example if I use one application compiled for 2MB flash and its save configuration at last flash sector and then I use application prepared for 4MB flash it may read board configuration from different address (which is invalid).
Is this my personal feeling or is it true?