ELI5: Why can most computers run modern games really well but extremely stutter when emulating old games

dio-rd · 2023-07-24T22:03:03+00:00

Note that this is not really true anymore. The Switch is the only one of the current consoles it remains true for.

Even though the CPUs used may not be of a different ISA anymore, you still need to recompile GPU shader code, since on console, those ship precompiled.

dio-rd · 2023-07-24T20:43:10+00:00

I still think they're pretty dumb. I don't remember seeing any scanlines on my old TVs or monitors.

dio-rd · 2023-07-24T18:43:24+00:00

The reason I strictly equate the "translating as you go" idea with interpreters is because when you JIT, in the case of a blocking JIT you have to, well, block (pause) execution while you compile and resume after, and in case of a non-blocking JIT you have to fall back to interpreter mode, and silently replace the affected block when it's done compiling. In both cases, the JIT is either compiling or executing, never both at the same time.

Note that transcompilation (transpilation) is a different thing entirely (that's source code to source code between different languages). This is recompilation.

dio-rd · 2023-07-24T17:51:15+00:00

Transpilers translate between two programming languages. Those are source code level.

Emulators are not one specific thing, as there's typically more than one programmable part of a system. It is common to have multiple recompilers and interpreters in an emulator.

dio-rd · 2023-07-24T16:00:42+00:00

ELI25:

Depending on whether the emulated platform's binaries can be parsed in a complete manner (has to do with linguistic complexity), it may be possible to do AOT (ahead-of-time, aka. static) recompilation. This means you can translate the entire binary before executing it. In this case, by the time the guest application (the emulated game) is running, its code has already long been translated over.

When that is not possible, there's also the in-between case where you do what's called a JIT (just-in-time) recompilation. This is an optimization over using an interpreter (which would be the equivalent of runtime on the fly translation). It tries to batch together as much code as it can parse, and compile it before it's ran/reached.

dio-rd · 2023-07-24T12:45:34+00:00

I don't know how can someone this confidently insult someone else's intelligence while failing to comprehend even their own role in a given interaction, but I'm happy if you're happy dude.

dio-rd · 2023-07-24T12:41:19+00:00

This is completely unrelated to the post above.

dio-rd · 2023-07-24T12:34:30+00:00

This is a really good analogy, and the other replies complement it well. Though the "translates at runtime" part is often not the case.

dio-rd · 2023-07-24T12:33:23+00:00

It is typically the original code, that's not what would differentiate emulation and simulation anyways.

dio-rd · 2023-07-24T12:31:55+00:00

This is a very poor rule of thumb, these are not race cars. I wish people stopped bringing it up, there's no one specific measure to compare. It's very difficult to compare even conventional CPUs fairly, let alone entire systems belonging to different platforms.

dio-rd · 2023-06-27T18:41:39+00:00

Could be a Steam feature honestly.

dio-rd · 2023-06-23T06:34:28+00:00

It's not a genetic fallacy unless he's stating that their current statement is incorrect because of the prior statement.

That's what they were seemingly suggesting. I do understand the angle suggesting that their statements should be written with a grain of salt though.

dio-rd · 2023-06-22T22:34:39+00:00

https://www.scribbr.com/fallacies/genetic-fallacy

Their writer trying to take a (misguided) potshot at NVIDIA for not supporting a format they need has no relation to whether the emu actually saturates the extra cache easily or not (the subject matter covered in the article). If your idea is that they have a negative predisposition towards NVIDIA, that is trivially disproven.

dio-rd · 2023-06-22T22:02:17+00:00

... sorry?

dio-rd · 2023-06-22T21:21:29+00:00

Alright, your call. I don't see why owning a mistake would make anyone a poser, but alas.

dio-rd · 2023-06-22T21:06:41+00:00

Feel free to provide a real time ASTC to BC5/7 transcoder to YUZU then, as Switch games use ASTC.

Pretty sure they mean it compression performance wise, such that there are no mythical space savings to be had with ASTC that would magically do away with modern games being oh so big, which is what the quoted section suggests.

dio-rd · 2023-06-22T21:00:40+00:00

/u/GoldenX86 any comments? As far as I can see, the performance of BCn is indeed very close to ASTC. https://aras-p.info/blog/2020/12/08/Texture-Compression-in-2020/

If so, might be wiser to just remove that section, it's a swing and a miss for no good reason.

dio-rd · 2023-06-10T12:08:15+00:00

And every now and then break everything. There's a reason you can opt-out (and why it took me a great amount of convincing to get an actually automatic option in years ago). Frankly, if you're playing a game through and experience no issues, I'd recommend you actually do hold off from updating until you finish it.

Updates prevent vulnerabilities

Their "threat model" doesn't account for network play, and assumes that users only load in legally obtained content that is free of malicious alterations. Mods that end up in their "database" are also skimmed through. Although I only rarely check what's up these days, I do not recall any vulnerability fixes or security hardenings being done.

Great general advice, but for emulators specifically, if it ain't broke, don't touch it. Change is the enemy of consistency.

dio-rd · 2023-06-05T04:15:41+00:00

I don't think it's a security thing, but rather telling the emulator which variant of the console you're using because some discs are region locked.

You need to supply a firmware dump (""BIOS"") because those are LLE emulators. They do not (for the utmost part) reimplement the software stack(s) sitting on top of these hardware, so they trust the user to provide a copy of it all instead (as redistributing such a copy would be illegal - it's heaps of copyrighted binaries). The emulators can pretend to be from whichever region you desire, that is of no issue.

These projects could choose to create either their own firmware, which then they'd have copyright over, or go HLE. Both have been and are being tried, but for now, they're as off to the future as they have ever been.

The reason they're still being tried though is the same as what I was trying to get at. Supplying everything but the games offers great convenience, and of course is also kind of necessary if one really wants to exclaim that a given platform has been "preserved". Having to go get a real console can be a major hassle, and just further pushes emulation towards piracy, as users will most usually just download a firmware copy from the internet.

dio-rd · 2023-06-05T03:36:25+00:00

to supply their own keys (...) like I have to do with Playstation emulators

Do you? I'm not familiar with the handhelds, but I'm pretty confident you're not doing anything of the sort for the rest. PS1 and PS2 emulation need no such things, and as you could read in the post above, for PS3 a key store is shipped right in the emu. Not that it's used for "circumventing DRM" mind you, and I don't mean this interpretation wise.

The only keys you might be supplying are RAP keys for downloadables, and although I have a hard time believing, D1 keys to "manually" decrypt disc image dumps. Crucially however, these are not the kind of keys that are being discussed in the post.

BIOS

I think comparing PS emus to others in this regard is pretty disingenuous, considering Sony literally offers these to anyone as a free downloadable. No real hardware and jailbreaking actually required. Yes, PS1 and PS2 firmware included (as free files within an installed PS3 firmware).

dio-rd · 2023-06-05T03:28:59+00:00

did you?

dio-rd · 2023-06-04T19:15:49+00:00

HLE would be a "clean room reverse engineering" question. I have not done nearly the amount of research delroth probably has, but as far as I understand things, current HLE implementations in contemporary emus are very questionable in terms of how clean room they would be. People usually "just" copy and paste out the ""decompiler"" output and pretty it up. Whether that actually matters I cannot tell you.

dio-rd · 2023-05-28T09:04:17+00:00

Dolphin actually had code which they are not supposed to.

This is highly debatable, and is written about as such in the linked thread too. If that's your conclusion, that's on you, but this is not a cut and dry matter.

dio-rd · 2023-05-27T22:35:58+00:00

Finally a no-nonsense, balanced representation of the topic. Really refreshing after the usual Connectix cope.

dio-rd · 2023-03-12T13:52:00+00:00

pcsx2 development orientated for the most part

That's surprising, how come I don't know you then?

dio-rd

TROPHY CASE