I am looking for an inexpensive single board computer that I could program in assembly language, using limited facilities to load the object code from a PC and simple I/O peripherals. I want to have an assembly program that writes in RAM some code and then branches to execute it. Arduino would probably be my best choice, as far as system simplicity suitable for assembly programming goes, but it has a Harvard architecture and it won't allow me to execute from RAM. I probably could write an interpreter of op codes written in RAM, but it is a very complex solution. Years ago I was using a Von Neumann architecture 8 bit CPU which could branch execution to any address, no matter whether it was mapped to ROM, RAM or whatever. This is what I would like to do now.
Any suggestions on workarounds with Arduino or of non-AVR Arduino boards based on Von Neumann architectures I might use?