Which is the Most Accurate NES Emulator?

[ShaneM]

I'm not much of a hardware man but I was wondering which emulator is the most accurate as in real-time?

I use FCEUX most of the time when I hack (2.2.2), but I really feel Nestopia UE is the most accurate one. Any opinions or information would be greatly appreciated. (Well, accurate as in NES/Famicom and FDS.)

EDIT: Oh yeah, let's include PAL NES, too, since FPS is different.

[Bregalad]

Nintendulator is the most accurate, and Nestopia the 2nd most accurate.

EDIT: Oh yeah, let's include PAL NES, too, since FPS is different.

Not only the FPS but ALL TIMINGS are different, and also some other things, mostly fixed bugs from the NTSC version.

[lidnariq]

Fhorse has been going to a lot of effort to make his punes awfully accurate. I suspect it's surpassed Nestopia by now.

I still use Nestopia UE, though.

[ShaneM]

Nintendulator is the most accurate, and Nestopia the 2nd most accurate.

EDIT: Oh yeah, let's include PAL NES, too, since FPS is different.

Not only the FPS but ALL TIMINGS are different, and also some other things, mostly fixed bugs from the NTSC version.

Yes. But what specifically makes Nintendulator more accurate than Nestopia? I hear Nestopia's accuracy is at about 97%. Does it support more mappers or is it something more technical?

[MottZilla]

I don't know how you say something is 97% accurate. That really doesn't make sense to give it a number. How was this number calculated, or was it just pulled from nowhere?

We have extremely detailed information about how the NES behaves these days. If you very carefully followed every little detail you'd have an extremely accurate emulator. Most NES emulators are far better than what was available over a decade ago just because of the wealth of information we have gained.

Another point to be made though, why does it matter to you which is the most accurate? Are you developing new software? If you are, I can definitely see wanting to find the most accurate emulator with good debugging features. If not that, maybe I could see you wanting the best compatibility. But even with just a basic level of accuracy you can probably support 90% of licensed games. The more precise accuracy tends to be for a very small percentage of games to work properly. Games you may never play anyway. So if you are just playing games, you're better off looking for the emulator that has the features you like best and works best on your hardware.

[tepples]

I wonder if someone's using compatibility with ROMs specifically designed to exercise edge cases, as seen in this chart, as a proxy for "percent accuracy". I wrote other thoughts on this in another post as well as the "Accuracy" article on the wiki.

[ShaneM]

I don't know how you say something is 97% accurate. That really doesn't make sense to give it a number. How was this number calculated, or was it just pulled from nowhere?

I borrowed that number from Koitsu. (See below.)

Reminder to folks: Nestopia plays, oh I don't know, ~97% of all games reliably, so please keep that in mind. [/url].

Found here at: viewtopic.php?f=3&t=11594#p133332


Also, I wanted to test accuracy for my FDS hacks, as I wanted to see if they would work on real hardware if GAP and CRC data were added back. That's why I wanted one with accuracy. Counting that no FDS emulators are accurate, an NES one (with FDS support) with close accuracy would be enough.

[thefox]

I don't know how you say something is 97% accurate. That really doesn't make sense to give it a number. How was this number calculated, or was it just pulled from nowhere?

I borrowed that number from Koitsu. (See below.)

Causality: If an emulator is accurate, it is able to run many games. However, just because an emulator can run many games doesn't mean it's accurate. It's trivial to make an emulator full of hacks to get games to run.

That said, Nestopia really is quite accurate. FCEUX is not super accurate, but I still use it because it runs fast.

PAL NES emulation is quite a bit behind NTSC NES emulation when it comes to the fine details. The main reason is that there are no known commercial games that exploited the differences between the machines beyond the obvious ones.

[Sik]

Causality: If an emulator is accurate, it is able to run many games. However, just because an emulator can run many games doesn't mean it's accurate. It's trivial to make an emulator full of hacks to get games to run.

Even without any hacks it means nothing, for the simple reason that games rarely exploit the most extreme corner cases of the hardware.

[Bregalad]

As far as I can remember PAL emulation was a bit off in Nestopia but was mostly correct in Nintendulator. It's things like jittering being a few pixels off and something like that. I might have changed with more recent updates, though.

[tepples]

FCEUX is not super accurate, but I still use it because it runs fast.

That and FCEUX has a debugging version, unlike Nestopia, and debugging works well enough under Wine, unlike Nintendulator. If you're just trying to develop or reverse engineer game logic in a program that doesn't exercise edge cases, FCEUX has an essentially perfect CPU and a good enough PPU.

[x0000]

Which is the Most Accurate NES Emulator?
Not an easy question to answer. All the latest emulators tend to be very accurate, but I can highlight a few:
-- Nestopia
Can run almost any game. However it is not the best emulator in terms of accuracy. It has problems with IRQ processing, audio processing, DMA, video processing, PPU/CPU sync.
-- Nintendulator
Was really a revelation for me. It is written in C++ and the source code is really straight-forward, almost like asm. From that I could really see that the author understands very well how NES operates internally (it matches my vision in most details at least). However, it has a lot of inaccuracies too (IRQ processing, unofficial opcodes, audio processing, DMA, PPU/CPU sync). But it has a very good PPU, I must give a credit for that.
-- puNES
Has a closed source code, thats too bad. But it is the most accurate emulator I know, especially when it comes to APU. There is still work left to improve PPU and maybe to implement some missing details for the variants of NES (NES PAL, NES NTSC, FC, Dendy, other clones).
-- FCEUX
Does not have a good accuracy, but is very useful for debugging and stuff.

I did not research this closely, but it can give you some ideas.

[tokumaru]

Like I always say, running a large number of games is not a sign of accuracy. Commercial games (and newer homebrew games) are finished programs, which have been tested and bug fixed for release. This means that they are (usually) well behaved programs, that do most of their work according to the book, so a higher level simulation of the system is often enough to support them well. Things are very different during the development of a new game: you'll find yourself writing to wrong memory locations, extrapolating VBlank time, forgetting to initialize registers... and that's when accuracy is really needed, otherwise those problems might go undetected if the emulator is too forgiving with the little details.

[Ti_]

Nintedulator helps me to find bug ,when I sent data on scanline '-1' without screen off. , so I vote for it.

[Myask]

That and FCEUX has a debugging version, unlike Nestopia, and debugging works well enough under Wine

The Windows-specificity of the...well, pretty much ALL the features, despite FCEUX allegedly being multiplatform, really irks me.

It strikes me that Mednafen isn't even on your wiki's list of emulators that do NES.
It has debugging features, rerecording features, memory-search features, albeit a bit user-unfriendly...and actually has these features on the linux version.

But, I haven't worked long enough with it/NES coding to really know its full accuracy. TASvideos seems to rank it middling at best. It doesn't seem to do the graphical tricks on Covell's Game Genie Decoder, instead showing green screen most of the time.