I'm no authority on this stuff, but I don't think it has to be one single universal ISA for everything. In the same way I can compile my C program to run on x8

I'm no authority on this stuff, but I don't think it has to be one single universal ISA for everything. In the same way I can compile my C program to run on x86 or arm, I can design it to interface with two different possible storage device architectures, if I want to.