[mcmustang51]

I found a program called FC2SMC that auto translated some basic roms...
How hard would it be to port games?

[Jorpho]

At the risk of stating the obvious: if it was remotely easy, lots of people would be doing it already.

[furrykef]

Probably not too hard if you have the source code or (more likely) a good disassembly. Nintendo's done it -- Super Mario All-Stars's code seems to be the NES games' code with new SNES parts bolted on. Their port of Wrecking Crew bundled in with Wrecking Crew '98 definitely is. It'd still take quite a bit of work and you'd definitely need to know lots about ASM for both systems.

As for automatic conversion, it's never really going to be practical, I'm afraid.

[Joezilla2014]

Its easier with converting nes to gba, why would it be hard to convert nes to smc if gba is 32 bit?

[KingMike]

The amount of bits doesn't matter. If the hardware isn't similar enough, it won't be easy to convert.
The two are similar enough that WITH source code it would be reasonably easy to convert (you could adapt the graphics stuff probably but sound would need to be completely reprogrammed), but WITHOUT it would probably be a lot more technical work (especially when mappers figure in).
You can't convert SNES to Genesis even though both are "16-bit" because their hardware is completely different.
I assume by "converting NES to GBA" you mean drop the NES ROM into an emulator that's already been written.
(and no, the SNES is not powerful enough to run an NES emulator)

And wow nearly 4 year bump. I think it would usually be better to start a new topic.

[Bregalad]

Its easier with converting nes to gba, why would it be hard to convert nes to smc if gba is 32 bit?

It's not converting it's emulating. That's two completely different things.

At the risk of stating the obvious: if it was remotely easy, lots of people would be doing it already.

Not to mention Nintendo originally planned for backwards compatibility but gave this up, there's a good reason to this.

[KingMike]

From what I heard, the "FAMICOM" button on prototype SFCs wouldn't have been a Famicom emulation mode but a video passthrough mode, intended to be used with an unreleased companion Famicom revision (an AV model like five years before the one that did come out).
As the proto SFC seemed to have both video input and output ports.

Although I wonder if that would've required both consoles to be plugged in and powered on, which I don't think is an advised practice.
(in the US, Nintendo would've expected players to use RF at that time and chain the connectors together. So you could turn both on but probably shouldn't.)

[Jorpho]

It is probably worth mentioning SMB4MD by Mairtrus, a port of the original Super Mario Bros to the Sega Genesis.
https://www.youtube.com/watch?v=Nz8s9xCYguA
http://devster.proboards.com/thread/613

But that came out years ago, and no one has made anything like it since, if I'm not mistaken.

And there's also Mega Man for the Turbografix, but again, there aren't very many ports of that nature.  The TG16 CPU is apparently very similar to the NES CPU, but that doesn't necessarily mean that porting games is trivial.  (People aren't running Neo Geo games on the Phillips CD-i, after all.)
https://www.youtube.com/watch?v=kKP5lRoa4Sc

[KingMike]

There are a couple of NES ROM conversion multi-carts in the PCE HuCard ROMsets.

But those are, again, only first-gen no-mapper games which are comparatively small and easier to make a conversion of.

[Psyklax]

The TG16 CPU is just a newer revision of the NES CPU, with a few new opcodes here and there. Thus, converting NES games to it would be relatively painless, other than the graphics being done a bit differently. But as KingMike said, early games are one thing, but ones with advanced mappers could be a challenge. Not impossible, but like many things like this, I don't see why anyone would bother.