I wonder if I can use SPI memories as system RAM/ROM (I mean, instead of the standard parallel ones) and if yes, how can I do it?. This would, of course, be considerably slower but we could instead have much more memory space. Also, it is easier to expand memory on a SPI bus.

There is plenty of info/code, like C libraries and so, to use these kind of memories, but this works once you have started up your system running from an internal or external parallel memory.

The questions: is it possible to use SPI memories to run code? Not just storing data but really running code. Do we need to modify the compiler?, the startup? or..?

Regards