No, they are not generally based on CPU emulators. FPGA emulators are more accurate than software based emulators, in part because they don't have to do gymnas

No, they are not generally based on CPU emulators. FPGA emulators are more accurate than software based emulators, in part because they don't have to do gymnastics to awkwardly emulate things that are easily done in hardware. For example, the documentation for Amiga's custom chips specifies which cycles various DMA activity takes place. Replicating that in hardware is quite easy (just a few comparators wired up to a counter), but it's hugely expensive in software which leads to all kinds of nasty hacks to replicate behaviour games rely on. It's similar with CPUs. CPU manuals from the 1970s and 1980s often specify the exact cycle counts for instructions while having simple bus interfaces and no caches. Coming up with cycle accurate hardware for these CPUs is not all that hard. The Amiga is the last machine I ever had for which I was able to get complete specifications and schematics for and understand completely. Once the 386/486 came along, documentation of SMM mode and other internal details became restricted. Modern computers have so much hidden firmware that understanding the entire system is virtually impossible. In contrast vintage 8/16 (and some 32) bit machines can be completely understood by a single determined individual.