[d66]

That's a fair point.

A few of us have been discussing a modified Varvara spec that limits the system to a smaller amount of memory (e.g. 32k, 16k, or 8k). I think with a spec like that it would unlock many implementations that are not currently practical.

[kragen]

I think a more important consideration for currently produced microcontroller hardware is the ability to run from ROM, because then you can load your program into relatively abundant Flash instead of the much scarcer RAM. Some way of using virtual memory (take a look at Forth's approach, which doesn't require hardware support but doesn't work for code, only data) would also make a big difference. All of this doesn't necessarily depend on native-code compilation; microcontroller memory is a much more tightly pinching shoe than microcontroller speed.

[d66]

It wouldn't be idiomatic Uxntal but there's a relatively simple modification where load/store is from RAM space but jump/pc is from ROM space. For a subset of existing programs it would work fine, although the assembler would need some modifications to make the memory layout(s) a bit clearer.