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Why isn't a DS emulator possible?

Discussion in 'iOS Emulators' started by Jonttu, Jan 1, 2008.

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Jonttu New Member

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I know, I read the sticky, but why not? Maybe now people don't completely understand the iPhone, but would it be possible in the future to make the emulator? On Zodttd's forum, Blueberry and Zod himself made a couple excellent points on why it's possible.
Blueberry:

Blueberry said:

There is absolutely no reason I know of why duel processors would make emulation impossible. Sure, a Nintendo DS emulator is possible, but not likely for at least 6 months to a year by my estimation. In the server world, it's extremely common place to have one physical server, with one single core cpu, and have that cpu, as well as resources like RAM, Hard Drive space, and network access, split in to many virtual servers. Inside those virtual servers, a real (usually unix) operating system is installed and run just as if it was running on a real server. This in effect allows a web hosting company to buy one expensive server, and slice it in to little pieces, suitable for each user's needs. And for this to work, each user has their own virtual CPU. This 'virtualization' is done using some amount of Dynamic Recompilation, the same technology already emulating the single CPU of the Gameboy Advanced, and in fact, if you look to your iPod while it's running gpSPhone, you will notice that the CPU is not consumed by the Gameboy OS, it is in fact running both the Gameboy OS and application, as well as the iPhone OS X, at the same time, on the same single cpu. I'm sure you can also imagine that if you opened a Gameboy emulator twice on a PC, and loaded different games in both, it would be emulating two completely separate CPU's on your computer, regardless of how many individual CPU's and CPU Core's your host computer has. The iPhone OS is a multitasking OS, just like Mac OS X on desktop computers, and is just as capable of things like this.

and

Blueberry said:

The Nintendo DS uses ARM processors, like the iPhone. So it's more an issue of 'virtualization' than 'emulation', where a NDS emulator on the iPhone platform would spend its time emulating various hardware outside of the cpu, such as the sound and video systems, as well as the cartridge interface and controller, and touch input. This is unlike the Playstation, which uses a totally different CPU architecture and thus requires all game code to be emulated (the never ending battle with DynaRec). It's wrong of me to compare two different architectures, but in the x86 world, virtualization has been perfected to the point where you can run one OS inside another using software like VMWare at near realtime speed. There could very well be something limiting about ARM's design which would make these near real time speeds unreachable, but for NDS emulation, realtime isn't needed. The NDS has a total of 100mhz processing power, split between one 33mhz, and one 67mhz arm core. The iPod Touch on the other hand is more along the lines of 400mhz. Maybe knock off 100 for OS stuff, and there is still 200mhz left to handle CPU virtualization and hardware emulation. So it could very well be possible, but this depends greatly on how powerful the iPod's Graphics Processor is. The NDS has a graphics processor capable of 2D on both screens and realtime 3D on one screen, both at 256 x 192 resolution. It seems pretty reasonable, and the iPod Touch could maybe just cut it, but we really don't know enough about the capabilities of the iPod's graphic's processor to know with any certainty. Until we find out, don't expect anyone to bother attempting a NDS emulator. Hopefully we'll be finding out this information in February when the Apple iPhone SDK is released.

as well as Zod's comment:

Zodttd said:

I know little about virtualisation but I'll give it a go. Virtualisation is used when the architecture of the emulated processor and the target processor's architecture match. There are time's when virtualisation can't be used even when both arch's match though. That is why Exophase most likely used a dynarec in gpSP over virtualisation for technical reasons beyond the scope of this discussion. When doing virtualisation, to put it in more simple terms, you aren't really emulating the processor's instruction set (think assembly here), but instead you emulate the system around the processor where it interacts. You emulate (map) the memory ranges, and hook into external devices like a flash memory handler and video layer. Virtualisation is generally much faster than a dynarec. A dynamic recompiler (dynarec) is like a super-charged interpreter. Where an interpreter parses a ROMs bytecode and emulates each instruction one at a time every single time it comes up, a dynarec does things differently. The dynarec method basically rewrites (translates) each processor instruction from the emulated system to a native instruction set of the target machine, all in a buffer. That buffer is inside a translation cache which allows it to be executed directly without the overhead of the translation process. By reducing the overhead needed by the dynarec's blocks of code in the cache, and getting the translation as tightly optimized as possible, you get very good performance increases. Dynarecs seems to be about twice as fast as an equivalent interpreter. When it comes to the DS, it can be emulated on the iPhone...nothings stopping that from being done. What it will take to get it running at decent performance is debatable though. I must say that the iPhone and iPod Touch only run at 400MHz (412MHz depending on the firmware). And each blit to the screen makes Springboard take up to 20% CPU time. This Springboard cpu usage is very high and can be why the 400MHz ARM1176 used in the iPhone is running things slower than a 266MHz ARM9 GP2X.

Any arguments against their comments?

Jonttu, Jan 1, 2008

#1
doodoobrown1 New Member

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i hope the ds emulater comes soon

doodoobrown1, Jan 1, 2008

#2
TheRapture New Member

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ds has dual processors... iPod touch doesnt

TheRapture, Jan 1, 2008

#3
Virtualball Well-Known Member

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That means nothing, there are DS emulators for single-core computers...

Virtualball, Jan 1, 2008

#4
Mindfield New Member

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It isn't impossible. It would just be slow. It uses two ARM processors: An ARM9 at 67MHz and an ARM7 at 33MHz, plus a 3D processor and two 2D processors (one per screen). Even with dynamic recompilation, you're likely only to run it at maybe half speed if you're lucky.

Incidentally, while it uses similar ARM processors, the iPhone/Touch use an ARM11. Not precisely the same thing, so virtualization is not possible.

Mindfield, Jan 1, 2008

#5
Bernstein229 New Member

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I would still use a DS emulator even if only three games were playable.

Bernstein229, Jan 2, 2008

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Mookler Banned

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Bernstein229 said: ↑

I would still use a DS emulator even if only three games were playable.

Something tells me you wouldn't.

Mookler, Jan 2, 2008

#7
Danls92 Super Moderator Emeritus

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Just because something can be emulated doesn't mean that it would run well.

It isn't a simple matter of 2> 1. It also has to do with processing power.

I remember somebody who knows about emulators (I wanna say zacaj, but I'm not sure) saying that it takes roughly 10x the processing power of a system to emulate it, and while the iPod might be able to process one of the cores, it would not be able to do both at even a slow speed.

That means nothing, there are DS emulators for single-core computers...

Keep in mind that the DS's processors are 67 MHz, (megahertz) whereas a computer's processor is usually in the gigahertz spectrum.

Danls92, Jan 2, 2008

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Mint-Berry Crunch Member

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Virtualball said: ↑

That means nothing, there are DS emulators for single-core computers...

yea the emulators are emulating BOTH processors because most single core computers are capable of doing both... with 67 mhz for one of them, its not that hard to do two on a comptuer. The ipod is only sporting a 412mhz single core arm processor so if an emulator does come out, it will suck... Not enough processing power

Mint-Berry Crunch, Jan 2, 2008

#9
[ß] New Member

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TheRapture said: ↑

ds has dual processors... iPod touch doesnt

Idiot, read the post.

[ß], Jan 2, 2008

#10

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