We had functional (HILO) models of MC68000, 68010, 68020, and a range of peripherals in '86-'87, along with the MC68121, which was just a 6803 with an integrated (6824?) 2-port RAM and flag register set. We also had models for several Intel processors/devices, but I'm not at all aware that the 8051 was among them. That same HP system had a "physical modeler" by means of which one could automatically generate a model for any part that would fit in one of the device's sockets, based on a set of vectors that were sent to it and the device behavior subsequently recorded.

I mention this just so everyone will know that this is not a new idea. It enables one to simulate the behavior of a circuit on a PCB even though multiple vendors' devices are involved. That's not the only reason one might want to do this sort of thing, but it's certainly one reason.

RE