[MBCook]

They don’t have to match.

As an example, what about a divide instruction. A machine without an FPU can emulate a machine that has one. It will legitimately have to run hundreds/thousands of instructions to emulate a single divide instruction, it will certainly take longer.

Thats OK, just means the emulation is slower doing that than something like add that the host has a native instruction for. In ‘emulator time’ you still only ran one instruction. That world is still consistent.

[anematode]

? That's not how Windows on ARM emulation works. It uses dynamic JIT translation from x86 to ARM. When the compiler sees, e.g., lock add [mem], reg presumably it'll emit a ldadd, but that will have different semantics if the operand is misaligned.

[cylemons]

You mean the locking would be done in software?