If you're soft real-time so that performance is a correctness issue you need more than Turing-completeness. I don't know off the top of my head if there's a na

If you're soft real-time so that performance is a correctness issue you need more than Turing-completeness. I don't know off the top of my head if there's a name for a constant-slowdown universal computer or if such a thing is possible.