I think something like this might be downright almost completely-doable with the state-machine already built-into SDRAM...

http://hackaday.com/2016/06/11/designing-a-single-instruction-computer/

I haven't looked into the details too thoroughly, I think the idea is to basically implement whatever instructions you wish to use as look-up-tables in memory. Well, hey, here's a shitton of memory ;) Then there's something about jumping, which sdramThing is *really* good at...

Of course, loading those look-up-tables is another thing entirely... FLASH makes more sense, but generally slower and smaller (in the parallel-interface format).

It's a curiosity I might revisit... (in fact, by writing this, I am already revisiting the idea of turning sdramThing into a CPU... something I vaguely thought of a while-back... here's something suggesting it's not only possible, but even implemented in different forms)