Hey!
Is it possible to emulate the powerpak?
I mean, the loader with someromson there?
Yes it's theoretically possible to emulate the PowerPak, but emulating the FPGA is definitely not technologically practical (or humanly possible to reverse engineer). If you just want an emulator with NES-side ROM loader, it would be smarter to whip up a multi-cart style menu which writes temporary emulator registers to select the mapper/configuration info and the massive game storage ROM offsets.
That sounds about as practical as writing an emulator for an emulator. In fact, it sounds exactly like that.
I wouldn't mind PowerPak emulation, just so I could hack a few things in the boot ROM that annoy the hell out of me.
Then how about we get into emulating the interface?
It could probably be fiddled with if FCEUX and a Lua script was used to poke and read the NES's memory.