Yeah, that would work _a_bit_ with some ugly tricks. Like keeping the last written I/O regs in memory (which can be read then ...), on NMI, forcing 0xB0 to a known state (without messing up the "I/O register backup), being the ROM of the "freezer cartridge", but then maybe SP pointed there and it's a problem, etc etc. Things like used IM mode is hard to get even that. Also internal states, as I've written will not be saved, the exact scanline/LPB, etc ... Even with these serve limitations, it's kinda hard to do this in a hardware. And for sure, this kind of snapshot is "not portable" ie it's a problem if someone wants to load a machine (or even the same one having modification ....) with different ROMs, RAM amount, etc etc. I would say, it's not impossible but with very serve limitations and some ugly complex logic. For sure, it can be done, if you implement a whole Enterprise-128 in an FPGA, what Chameloen does (if I know well, it was born from the FPGA64 open source project once, though now it's not open source as the Chameloen). But then you have a whole computer in FPGA ... Not even needing a "real" Enterprise hardware ...