Ask Bibin about his DSi

[palmertech]

Considering the DSi has a brand new core, I doubt there is any soul of the GBA left, save the bits that handled sound and such in DS games.

I could be wrong, though.

[XCVG]

As far as I know the ARM7TDMI is necessary for DS games to run, meaning it is at least emulated. Also, the DS graphics core is an upgraded version of a GBA core and a 3D accelerator put together. Sound is software generated I believe. So yeah, it would be insanely difficult, but possible.

[palmertech]

The GBA ARM7 is not needed to run DS games. A lot of games offloaded sound to just a few things GBA side, though.

The DSi lacks most GBA parts, unlike the GB Micro, they just did a complete re-design. The only GBA components in there are the ones needed to run the sound on certain games, and if it were as simple as running it on the upgraded DS core, Nintendo would have done that in the first place to save costs on the DS Lite. There is no way through hardware to run GBA, and it would be a miracle of coding to make a GBA emulator that would run on the DSi.

"Insanely difficult" it is not, it is just flat out impossible.

[XCVG]

That's news. I always assumed that the DS used the '7. I guess not. That increases difficulty astronomically, because the ARM9 (11?) in the DSi is similar in architecture but completely different in implementation. So it's possible, but it's like porting a 360 game to PC in terms of difficulty. The video system probably got a redesign too.

This alone is a reason for me not to buy a DSi. I like my GBA games, and there's no way I'm carrying around 2 devices. Apparently some DS games don't run either. The DSi has good features but with the tradeoffs and price tags I'm just not going for it.

[nitro2k01]

That's news. I always assumed that the DS used the '7. I guess not. That increases difficulty astronomically, because the ARM9 (11?) in the DSi is similar in architecture but completely different in implementation. So it's possible, but it's like porting a 360 game to PC in terms of difficulty. The video system probably got a redesign too.

So much misinformation...
The DSi is using the same ARM9 and ARM7 as the older DS, but with the capability of running at two times the clock speed. The confusion comes from Bunnie's blog post about the DSI where he speculated what might be in the DSi:

The markings on the CPU package yield no clues about its performance, but my guess is that any ARM9 or ARM11 CPU manufactured in 2007 would have a performance around the 266-533 MHz range.

This has become the standard speculation, and apparently it still lives on still 6 months after the (Japanese) release date. If you look in the comments of that post you'll see that even Bunnie himself is baffled at how fast the rumour spread, and he points out that it's just speculation from his side. (Here)
What is not in the DSi, apparently, is the GBA core. But apart from the additional GB classic sound registers, everything is still there, just at different IO addresses. This doesn't help you because you still can't run a GBA ROM straight away. But it does help Nintendo since it makes it easier for them to release a development kit that developers can use to port GBA games to DSi and sell the games as DSiWare.

Apparently some DS games don't run either.

Source?

[Bibin]

This doesn't help you because you still can't run a GBA ROM straight away. But it does help Nintendo since it makes it easier for them to release a development kit that developers can use to port GBA games to DSi and sell the games as DSiWare.

"Birds and Beans" is a good supporting argument for this.

Wii is to GameCube as DSi is to DS.

[XCVG]

So basically you are saying that I'm right and Palmer is wrong

Of course I am joking. If this is true then it is theoretically possible to patch GBA games to run. We just need someone to work on it. No, don't look at me. I fail with this kind of stuff.

[nitro2k01]

So basically you are saying that I'm right and Palmer is wrong

You were both half correct actually... And I think palmer was more correct than you. However, you were actually unintentionally spot-on about something with a little change.

because the ARM9 (11?) in the DSi is similar in architecture but completely different in implementation.

The ARM9 on the DS vs DSi are actually identical as far the code is concerned, except for an new area of IO ports which is only available in "DSi Mode". When booting an old DS game, the firmware shuts off access to all the new features and then loads the game.
On the other hand, the statement is true for GBA ARM7 vs NDS ARM7. The same CPU core is being used, but it has a completely different IO map, and a reduced amount of memory in GBA mode.

As for the ARM7 being used in DS games or not... If using the standard Nintendo devkit, the ARM7 is supposed to be redundant, given a faster ARM9 speed to account for the extra work. But I guess they realized that in practice it's better to keep things as compatible as possible.

[XCVG]

If the '7 in the NDS has a different IO maps, how do GBA games run? Is there some weird shifting going on?

[nitro2k01]

If the '7 in the NDS has a different IO maps, how do GBA games run? Is there some weird shifting going on?

There's a special register that tells the NDS to enter GBA mode. When that happens, the '9 is deactivated, and the '7 is disconnected from the NDS memory and IO map and connected to the GBA memory and IO. The speed is reduced to ~16 MHz and the CPU restarts from position 0x00000000 (Which at this point points to the GBA BIOS)

[XCVG]

Okay, got that. So it has a complete other RAM chip as well? Or a reserved space? Also, does it share the video processor with the DS mode hardware?

[Bibin]

So basically you are saying that I'm right and Palmer is wrong

Of course I am joking. If this is true then it is theoretically possible to patch GBA games to run. We just need someone to work on it. No, don't look at me. I fail with this kind of stuff.

No. Get out. They did not just "patch" games like Birds and Beans, but they did an entire port, where they took the original source code and rewrote portions of it.

[XCVG]

A port is not that complex when you think about it. The instruction set in the '9 is the same. Most of the addressing will have to be rewritten, obviously. The I/O code needs considerable changing. Yes it is a port, but it could be accomplished with a patch that replaces some (lots?) of the code.

[Bibin]

A port is not that complex when you think about it. The instruction set in the '9 is the same. Most of the addressing will have to be rewritten, obviously. The I/O code needs considerable changing. Yes it is a port, but it could be accomplished with a patch that replaces some (lots?) of the code.

Simply patching the game would not fix the plethora of introduced issues. Screen resolution? Different audio system? Input changes? ARM7 binary introduction? More than a patch would be required.

[XCVG]

A port is not that complex when you think about it. The instruction set in the '9 is the same. Most of the addressing will have to be rewritten, obviously. The I/O code needs considerable changing. Yes it is a port, but it could be accomplished with a patch that replaces some (lots?) of the code.

Simply patching the game would not fix the plethora of introduced issues. Screen resolution? Different audio system? Input changes? ARM7 binary introduction? More than a patch would be required.

Well you would have to patch all that. I know, you pretty much have to rewrite a lot of the game, meaning that if this happens it will only be for popular games.