μClinux on Ibex or CV32E40P?

[limone]

* Whereas Ariane (or CVA6) was built just to run Linux, it is not particularly optimized for one or the other. Since it is a 64 bit core, it is much larger (about 4x RI5CY), it is not really low power
* Whatever the core, the memory needed is MUCH MORE important actually. roughly speaking 5-10 kGEs is the size of 1 kilobyte memory. Basically 8kByte memory is one RI5CY core. (or 2kByte memory is one Ibex core)."

What is the lowest power RAM that could be integrated with an application processor?  

I found a relatively fast one: https://www.cypress.com/file/444201/download (20mhz)
SRAM seems like the goto way to boot an RTOS, but the size for many years has been too low for application processors: https://www.emcraft.com/stm32f429discove...-footprint

Could I put 8 of those 8Mbit FRAM chips together on a board/chip? Could 6MB boot linux? This has 6 SPI ports: https://www.top-electronicsusa.com/ama3b...17907.html

Or would I need to use a different interface, like Parallel? https://www.mouser.com/Semiconductors/Me.../_/N-4bzpt Some run around 1mhz, but I do not know if that is too slow to run linux. 

For IoT, it seems like speed is less of an issue:
https://eepower.com/news/sram-with-lowes...84ns-read/  

Recent products: 
https://www.cypress.com/file/451661/download
https://www.renesas.com/us/en/products/m...ower-srams

Edit: I realize integrated memory is probably more efficient than external memory, although I do not know if the SPI ports are low power enough to serve as a natural extension of the IC. Also, the Cypress FRAM appears to require high-speed SPI, and I'm not sure how many the Apollo3 board has. Also the transistors in the add-on memory are probably larger than the DDR5 sticks being made.