Pulling the long-time-portability lever one mark further, I suggest Bochs. It's slow because it doesn't use Qemu's dynamic recompilation, but on the other hand,

Pulling the long-time-portability lever one mark further, I suggest Bochs. It's slow because it doesn't use Qemu's dynamic recompilation, but on the other hand, that simplicity makes the job of future archaeologists easier.