Realistically, I suspect most of what people use computing devices for could be done with the following:
* 100 MHz CPU with a single 3-5 stage pipeline, a FPU, no branch prediction, no out-of-order execution, no kind of speculative execution
* A GPU with enough resources for 2D desktop composition (not necessary but nice to have) and a hardware-accelerated 1080p60 video codec, that can also be used for some light general-purpose workloads
* A crypto coprocessor
That's it.
@Anarkat Nah, doesn't have to be RISC specifically, more speaking of a general technology level.
I mean, an Intel 486DX4 meets the CPU portion of this description perfectly.
But, yes, there's a lot of 80s and early 90s RISC designs that also meet it.