If so is it possible for a third party to create a new device with a different bios that allows you to play n64 game hacks legally ?

Such as this mod for wwf no mercy

I assume the n64 is powerful enough to handle this hack with a new bios

to play n64 game hacks legally

Game hacks will never be legal depending on which device you play them on. Those games are intellectual property of their respective owners, and thus are protected by (most) laws from modifications. Nobody is going to sue you over playing hacked games anyways, so this can be disregarded. Even with a newly designed, legal console that doesn't infringe on any of Nintendos patents, if you want to play modded games, its as illegal as it was without that.

As to whether you could play this on an N64, correct me if I'm mistaken but unless the mod requires a resize of the original ROM (like some mods do), the only problems in getting this to play on an N64 is (disclaimer: since talking about legality, all of this can probably be considered illegal anyway):

- Getting it on a medium that the N64 can read, like a cartridge. I don't assume they are produced anymore, maybe it is possible to overwrite the content of another game?

- Getting past the lockout chip. I don't know whether hacking a N64 rom produces a game that is rejected by the lockout chip, but if it does, you need something to circumvent it.

- Performance. I don't know what this hack does exactly. If it just replaces some game content etc.. than it should be fine, emulators do just that; emulate the underlying hardware. Now it is possible today for old emulators to run at much higher speeds on current PC CPUs, but usually its the other way around. So chances are, if the emulator can play it, the console can too.

I'm not that technical expert on console hacking/modding, but I doubt there are many more factors to consider. Correct me if I'm wrong.

Forgetting about legal part for one sec, the original N64 is not powerful enough.

The characters' profile pictures are clearly way higher than what the N64 allowed. The N64 had just 1MB of VRAM and a 4kb texture cache. That's a 32x32 texture in 32-bit RGBA; and the reason so many games had choppy/crappy/stretched textures.

Those profile pictures alone are of much higher resolution and colour depth and cannot certainly be rendered in real time by the N64. It might be possible at very reduced framerate by rendering multiple times without clearing or taking advantage of deinterlacing. But also you have to account the limited space of the cartridge and the limited RAM. There are major challenges to account.

I'm sure it depends on your country, but modding a game or console for personal use surely isn't illegal.

Of course, anyone can still try to sue you, but that doesn't mean you've done anything wrong.

I'm sure it depends on your country, but modding a game or console for personal use surely isn't illegal.

In the USA, thanks to the DMCA, that ain't entirely so.

Consequences of the DMCA

We were discussing this in an earlier thread also created by the OP.

If so is it possible for a third party to create a new device with a different bios that allows you to play n64 game hacks legally ?

In my non-lawyer opinion, it is theoretically possible for a legit emulator software or emulating device to exist for some consoles, but you have to navigate a veritable minefield of legal issues by carefully jumping through all the right loopholes.

DMCA rulings support fair personal use actually. Even against Apple.

When one jailbreaks a smartphone in order to make the operating system on that phone interoperable with an independently created application that has not been approved by the maker of the smartphone or the maker of its operating system, the modifications that are made purely for the purpose of such interoperability are fair uses.

But, we're talking about creating a brand new device with no dmca protected code/hardware.

DMCA rulings support fair personal use actually. Even against Apple.

"Fair personal use" - is that your wording, or the courts?
What constitutes "fair", and what, in this ruling, is the definition of "personal use"?

If the court says you can jailbreak a smartphone in X and Y situation for Z purpose, we can't interpret that to mean we can do anything else that, to us, seems like it might sortof be kinda similar. The courts created a narrow exception to a broad rule, and you are using the narrow exception to argue that the broad rule no longer applies in situations not covered by the narrow exception.

Laws are strictly written, and unless a judge interprets it more broadly, we can't assume laws broadly apply in only situations we want them to, and narrowly apply in different situations when it benefits us.

But, we're talking about creating a brand new device with no dmca protected code/hardware.

I was responding to your post, where you said, "I'm sure it depends on your country, but modding a game or console for personal use surely isn't illegal."

Modding a game or console, by the very definition of modding, is not a "brand new device" and certainly is "dmca protected code/hardware." (depending on the console)

As for the OP's original question, which talks about a new device entirely, without modding, I do think it's theoretically possible, if you "navigate a veritable minefield of legal issues by carefully jumping through all the right loopholes."

And I went into detail about some of that minefield, and some of the loopholes, in the other thread.

I'm definitely not a lawyer, or any kind of expert in law - but I'm basing my opinions on a strict and literal reading of the few actual laws I've read and looked into. As I've mentioned in other threads, I don't approve of how far these laws have been twisted by corporations and the courts! I wish they'd get heavily rewritten. But if I'm going to make an honest attempt to understand what the laws actually say, I can't stop reading the first time I find a vague statement that I might be able to twist around to give me a pleasing result. I don't want to be my own 'yes man' telling me what I want to hear; I want to know what the truth actually is even if it isn't what I want it to be. I want to read it for what it says, not for what I want to pretend it says.

If there are actual laws that clearly contradict my current understanding, I want to know about them, to further my understanding. frob and I were discussing a part of copyright law, and as much as I wanted to believe his interpretation of it (which would directly benefit me if I agreed with it), a plain straight-forward reading, as literal* as I could read it, using common-sense* where necessary, gave me a completely different interpretation than what he was getting. Two intelligent individuals can make an honest attempt to read a document truthfully, and end up with diametrically opposed understandings - alas, but such is legal writing.

* 'literal common-sense' (i.e. interpret it literally, unless common-sense dictates otherwise) is the hermeneutic I use.