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melonDS aims at providing fast and accurate Nintendo DS emulation. While it is still a work in progress, it has a pretty solid set of features:
• Nearly complete core (CPU, video, audio, ...)
• OpenGL renderer, 3D upscaling
• RTC, microphone, lid close/open
• Joystick support
• Various display position/sizing/rotation modes
• (WIP) Wifi: local multiplayer, online connectivity
• and more are planned!
If you're running into trouble: Howto/FAQ
If you're feeling generous: melonDS Patreon
JIT beta builds and introducing myself
Dec 7th 2019, by Generic aka RSDuck
After all so much time has passed, it's finally time to do a release of JIT beta builds!
As Arisotura has stated in her last post, there's now another head working on melonDS. I'm Generic on IRC and RSDuck on Github.
For some reason I started messing with DeSmuME a bit more than a year ago, trying to write a JIT recompiler targetting ARM64, to improve performance on the Switch. After many struggles something working came to be, but it missed it's original goal of being fast for several reasons (see the link if you're interested).
After recovering from the disappointment I put my hopes into melonDS, but since it lacked any JIT compiler (besides the abandoned attempt by Arisotura herself) I wanted to start with a x64 recompiler. Skip forward a bit and the JIT started take on form. After taking everything apart and putting things more cleanly back together around the beginning of last summer things only got better, with most instructions being recompiled and the opening of the pull request on Github, which later got merged.
At this time the ARM64 backend was started this time avoiding my previous mistakes. With autumn it reached a similar level of completion as the x64 backend while both backends received some optimisations. Until this point we were catching up to DeSmuME but at this point started to surpass it. Here is where I want to thank all developers of open source emlulators whose dynarec I was eable to look into and especially the developers of the JIT of Dolphin. We're not only using their code emitter but they also gave me some great advice on IRC!
With some further optimisations of the 2D GPU emulation using ARM NEON instructions, most 2D games already run at fullspeed on the Switch, while most 3D games run at fullspeed with overclocking. The ARM64 JIT and the GPU optimisations are currently located in my own fork and are distributed by me in binary form on Gbatemp in an admittedly chaotic way.
I am very grateful to Arisotura for creating the emulator in the first place, as well as trusting in me and my work. For the future the already mentioned GPU optimisations are my current focus. I'm currently rewriting the old ARM NEON optimisations to be more clean and adding some additional ones which hopefully increase the performance a bit more. The logical step following would be a NEON 3D GPU backend. I have some more plans lying around, e.g. there is still one major JIT optimisation we're missing out on (fastmem).
So but now enough storytelling, here are the builds:
... read more
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Status update II
Dec 5th 2019, by Arisotura
First of all, things have been a bit shitshow-y, and involved a few bursts of depression, but, finally, it's there, I have my apartment now. I'm not quite finished settling here, but that's a big relief for now. Plus, the place is fairly nice! Except for the wall sockets being upside-down, but, eh.
Next, I'm being sucky at delivering a JIT beta. Thing is, unlike the DSi branch which was hacked together by me, the JIT branch is Generic's work, so I will need to take a while and get familiar with it.
In the meantime, I figured I would let Generic handle things himself. I gave him access to this blog and all, so he will be able to post a beta build, which he said he would do tomorrow.
I figure the best way to work with this long-term is to work as a duo. I'm less skilled on things like fast CPU emulation, and more skilled on other parts of emulation, so other people like Generic can complement me nicely there and together we can deliver an excellent product.
And, holy fucking shit, reconciling the JIT and DSi branches is something I'm totally looking forward to. At this point, the DSi branch already has several conflicts with the master branch (it's based off 0.8.1, so yeah), and, no idea about the JIT branch.
Immediately tho, I'm going to improve the OpenGL renderer. This means reorganizing some of the code so it's easier to work with, fixing some longstanding issues like the case of dual-screen 3D, and adding some filtering.
You can follow the progress in the appropriately named blackmagic_II branch.
Hell, even writing this post is taking me forever.
Also, today's Dec 5, and it's the general strike day. Seeing how successful it was, if they manage to keep going at this rate (and they totally intend to keep going), president Macron is going to have a hard time. But, this also means that certain things may be delayed, or whatever, so we'll see.
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Nov 17th 2019, by Arisotura
Not much to say these days, sorry about it.
Couple things though.
On melonDS, things are going to be mostly on hold until I manage to get a proper apartment and am all settled in and all. But, two things. First, Generic said that the JIT branch is ready for a beta release, so I'll be doing that. Second, as a next direction to take the project, I'm thinking about adding support for AR cheat codes.
I'll also be trying to fix the remaining issues with the OpenGL renderer, but some are going to be tricky. Also, things related to this renderer: I need to come up with a not-too-hacky solution for dual-screen 3D and upscaling, and to add support for filtering in OpenGL mode (including xBRZ or something of that ilk).
But, blegh. The apartment. I visited one a while ago, now I'm going to have to put together the paperwork and hope it isn't too late. There are other apartments I can try, but, hey, I liked that one. So, here's hoping.
Oh also, this is Nov 17, birthday of the yellow vest movement. French protest movement that started one year ago, was originally against a gas tax raise but turned radical and against precarity in general, which seems to be a common theme these days (thinking about Hong Kong, Chile, ...). Despite the fact that the movement as it is will not bring revolution, it seems to want to never end... (what kind of protest movement lasts one whole year?)
But we can see that it's having an effect on protests in general, they turn more radical now. Like recently, a student from Lyon set himself on fire out of despair after being thrown into precarity. Had that happened two years ago for example, nobody would have cared, it'd just have been "another depressive sicko attempts suicide, film at eleven". But instead, this sparked several student-led protests and blockades, including one that broke into the Ministère de l'Enseignement Supérieur.
Dec 5 is going to be the general strike, too. I first thought that would be lame, as most of these attempts were a while back, but, now, within the different context, this looks like it's going to be quite something. May also cause some trouble on my end, but, we'll see.
Anyway, happy birthday to the yellow vests. I've been following the movement closely, and even taking part in it, as it gave me hope when I was at the worst of depression, so this means a lot to me.
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When things turn out unexpectedly simple
Oct 20th 2019, by Arisotura
As I said in the previous post, melonDSi can't boot any DSi-enabled cart. I'd been banging my head against the problem for a long while, attempting to work out how the launcher on the ARM9 worked and why it was failing, but went nowhere. The code is a pain to track, relying on all sorts of threads and callbacks and things.
Shows that taking a break does wonders.
Just yesterday, I idly looked at that bug again. Reproduced the freeze, then pressed F11 (debug key printing some status to the console) a few times to see if I could see a pattern. The ARM9 seemed to exhibit typical 'idle thread' behavior; the ARM7 however, seemed to get stuck in a loop. A quick glance at my IDB of the firmware code confirmed this:
If you aren't fluent in ARM assembly, this function waits for the AES engine to finish whatever crypto operation it is doing, by checking the busy flag in AES_CNT.
But, in our case, the ARM7 got stuck inside this because, somehow, said busy flag remained set forever.
Some logging of AES operations shown that, while loading the game, the firmware would start a decrypt operation with a block count of zero. melonDSi didn't check for that case, and instead waited for data input that would never come (heh), causing the busy flag to remain set forever. You guess how this goes.
After quickly fixing this bug, I tried loading a cart game again. It still froze on a white screen, but the logs showed it was getting further. In particular:
UNIMPLEMENTED ARM9 NDMA3 START MODE 04, 04100010->021153A0 LEN=1 BLK=1 CNT=A4044000
That meant the game was actually booting, and attempting to load its data, using NDMA ('new DMA' implemented in the DSi) for whatever reason. NDMA start mode 04 is for cart slot DMA, which is triggered every time a data word is transferred from the cart.
... read more
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melonDSi beta release
Oct 15th 2019, by Arisotura
Apologies for the silent month. Things are shaking up here irl, as I'm starting that job, and looking for a new apartment, which is a bit of a shitshow.
Anyway, here we go: we present you melonDSi, in unfinished beta glory. The JIT beta will follow, but I first want to ensure Generic is comfortable with it.
The end goal will be to merge this with regular melonDS once it's in a better state, but, for now, we're providing it for the curious folks.
How to use melonDSi
BE SURE TO READ THIS BEFORE USING MELONDSI. You are using a beta release, provided with zero polishing and with a debug console. I expect that you know what you are doing to atleast some extent.
melonDSi will require several files to be dumped from a DSi. It's a bit messy right now, but we hope to come up with more user-friendly solutions in the future.
So, if you have a DSi, you might want to install unlaunch on it.
A quick rundown of the files melonDSi requires:
* bios9.bin / bios7.bin: DS-mode BIOS images. Those are the same as the ones from a DS. They shouldn't be required to get DSi software running, but melonDSi will refuse to start if they aren't present.
... read more
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2D accuracy: it's a rabbit hole too
Sep 14th 2019, by Arisotura
Yeah. I've been wanting to fix mosaic support in melonDS, and, well, got sidetracked (I know I still have to release the JIT and DSi betas).
Anyway, mosaic is a typical feature of old consoles with 2D engines, including the DS. It basically applies a pixelation effect to graphics, as shown here:
The basic idea is that the screen is split in a grid, whose dimensions are variable (configured by register 0x0400x04C on the DS). For each 'cell' in the grid, all the pixels are colored the same as the first (top-left) pixel. In reality, it's a bit more complex, as on the DS the effect can be applied per-layer and per-sprite, and you can even specify different grid sizes for BG layers and sprites, but fundamentally it's more or less the same thing, it pixelates shit.
Sounds simple enough, right?
It's a bit tricky to implement when you're trying to write a performant renderer, though. Which is more or less why blargSNES never supported it.
As far as melonDS is concerned, mosaic was implemented in version 0.5, but (among other silly bugs) it never worked quite right as far as sprites were concerned, especially when those use rotation/scaling. But, at the time, I didn't do much past the original implementation, mostly because I don't know of a lot of games that use the mosaic effect. The lack of test cases meant it stayed supbar.
Until, well, now.
First thing to do is to write some test cases for sprite mosaic. BG mosaic seems quite simple, even though I would still have to probe it extensively for edge cases, but sprite mosaic is a bit more oddball, as seen here:
... read more
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Sep 4th 2019, by Arisotura
About fucking time, I guess.
So what does this release bring? Well, we have been trying to address the issues present in previous 0.8.x releases (or sometimes even older releases, heh).
For example, I fixed the bug that was introduced with the new support for Ctrl+K type hotkeys. Basically, using Shift/Ctrl/etc as regular keys mapped to buttons was no longer possible. So, support for key mappings with modifiers was restricted to hotkeys. Meaning that using right Shift as R (as done by the default key mapping) should no longer cause input problems.
I have been trying to fix the issues we had with the framerate limiter and audio output, too, with moderate success. As I haven't been able to come up with a one-size-fits-all fix, there are now three different sync modes you can use, individually or together:
* Limit framerate: the oldschool framerate limiter. Although this is a revamped version that tries to average over several frames, reducing the likelihood of limiting too aggressively on certain games that internally run at 30FPS and are otherwise able to run fullspeed.
* Audio sync: synchronizes emulation to the audio output system. Seems to result in a bit more fluctuation in the framerate, but should prevent any audio stuttering.
* VSync (in the video settings dialog): synchronizes video output to your monitor's refresh rate. This only works with OpenGL, and currently only works under Windows (OpenGL support under Linux still needs more love). Also, DS games/programs may alter their framerate by messing with VCount, which VSync would be ill-equipped to deal with (unlike the two other sync methods).
I think most of the audio issues came from not properly syncing, which resulted in semi-regular overflows or underflows in the SPU FIFO, causing stuttering. The current audio output system cannot be precise enough to prevent those, as it works with small audio frames.
Speaking of which, I have also been revising it to use a more standard output frequency, in case some bad audio driver doesn't appreciate the previous frequency of 47340Hz. Now, it will attempt to run at 48000Hz, but it also allows SDL to specify another frequency if needed.
... read more
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Aug 23rd 2019, by Arisotura
Not a lot to say other than that I'm still trying to figure out how to fix audio output. And I hope the fix will work. It would be utterly soul-crushing if I spent all that time figuring out a fix and implementing it only to have it be a trainwreck for half the userbase or whatever. So... let's pray.
Also, on the DSi front:
I'm also unsure what to do. there are BIOS dumps out there that have been filled as much as possible, by dumping the lower half and adding back the known parts of the upper half that can be sourced from elsewhere, as seen there: http://problemkaputt.de/gbatek.htm#biosdumping . NO$GBA expects these particular dumps. I might want to adopt that method too, but I'm afraid such dumps are less complete than dsikeys.bin/initmem7.bin/initmem9.bin.
Opinions on this are welcome. I'll need to check how much of the AES keys is sourced from the BIOS, vs how much is needed to run shit like the DSi firmware.
For reference: dsikeys.bin contains all the AES keys, as extracted from the AES engine after an unlaunch boot. initmem7.bin and initmem9.bin are chunks of ARM7 WRAM and ARM9 ITCM that contain keys (RSA, Blowfish) and other shit needed for initialization, those are mostly (but not entirely) sourced from the BIOS.
On other fronts, all sorts of exciting things are being developed for melonDS! Those who follow repo activity may have noted that DLDI support is being worked on. Stay tuned!
Edit- comments about how "I don't give a shit about DSi emulation!! Work on the features I want!!" or "nobody cares about DSi" or whatever, are getting on my nerves. There are very good reasons to work on DSi emulation, so I swear that if this shit continues I'll be deleting comments and handing out bans.
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Progress on the DSi front
Aug 4th 2019, by Arisotura
The other front would be, you know, getting 0.8.3 good for a release. Which means, fixing the goddamn audio output system. Have been rather unsuccessful at that task for now.
So instead, I did what I typically do in these situations: procrastinate and work on something else.
In this case, the DSi front.
If you remember, this was at a point where it needed wifi initialization to be able to launch titles. I was stuck at a particular point of the init procedure, where it waited for something and I had trouble figuring out what. But, regardless, I set to work.
In the meantime, googling some of the strings present in the firmware's wifi code brought me to this Atheros driver codebase which is very close to what the firmware uses. This helped me a lot in figuring out how things work and what the firmware was expecting.
It's possible to boot shit from the firmware now!
Couple issues with this though.
... read more
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Jul 21st 2019, by Arisotura
Things have been slow lately, you may have noticed. Couple reasons to that.
I meant to fix a few of the issues we had lurking around, so we could release 0.8.3. I managed to fix some issues that caused random crashes on exit, then began trying to fix the framerate limiter. Thing is, it is directly related to the audio output code and the issues that has. So, yeah, I still haven't found a solution to that tricky problem.
I also need to struggle to keep some motivation at times. Looking at the patterns in how I work, it is likely that I have ADHD. I have yet to get diagnosed and all, but this wouldn't surprise me.
As you may have noticed, Github user RSDuck sent a pull request for the JIT recompiler. This is a bit of a tricky situation though. I don't want to have to deal with a situation where people make third-party JIT builds, but at the same time, the JIT isn't quite ready for general use, as we're still ironing out various issues with it.
However, the JIT is said to give a performance boost ranging from 30% to 100%, which is fairly nice, especially as there's room for improvement. RSDuck also said that porting the JIT to other architectures, like ARM, should be easy, so we might finally have Switch builds that run at acceptable speeds.
Or, also, Android builds. But, dunno. On one hand, this is a market I want to address, but on the other hand, history from Dolphin has shown that the Android userbase isn't exactly the nicest to deal with, so... yeah. And don't get me started on Android itself and the fun that coding for it is.
But first, let's focus on what we have in front of ourselves.
I'm going to try as hard as I can to fix the audio issues for 0.8.3 (and also add a vsync setting).
We will also be releasing beta builds of the JIT and the DSi branch, for those of you who want to mess around with things.
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