Hardware Homebrew GBARunner, the DSi and you

[fantasma_do_cu_cagado]

Im sick and tired of seeing these arguments over and over, how does Gbarunner actually work?

There's an arm9 and arm7 versions, whats the difference?, does the arm7 ver actually run on the arm7? how different is it from native?

Some ppl also claim the DSi removed the GBA hardware (ex), same say it has it (ex), and as far as i can tell, removing it is impossible since the arm7 is required as the I/O co-processor.
Which is it?

And how (im)possible is the idea of actual native GBA on DSi? (like open_AGB_firm on 3ds)

 

[ghjfdtg]

The DSi doesn't have the full GBA hardware and it's missing the physical cartridge slot. It does have the ARM7 CPU since it's needed for DS/DSi mode but it's missing a whole lot of other hardware like the GBA's PPU (picture processing unit). An upgraded variant of it is available in DS/DSi mode and is known as the 2D hardware. The APU (audio processing unit) is also different on DS.

The way GBARunner works is best described as a virtual machine. It runs the ARM7 code natively but whenever the game tries to access something that doesn't exist in DS mode (but does on a real GBA) it intercepts and emulates that part. This approach is very fast but it throws all the accuracy out of the window which is why GBARunner2 has so many compatibility issues. GBARunner3 uses a little bit of a different approach to improve accuracy but it's never going to be as good as native GBA hardware.

 

[Egoistamamono]

Yeah, DSi doesn't have GBA hardware like phat/lite, so what gbarunner2+3 does is virtualization or hypervisor. It looks like there are 2 versions of gbarunner2 because for DS and DSi, you can use gbarunner3 for better compatibility.

 

[RocketRobz]

Other questions have already been answered, so I'll answer this one:

There's an arm9 and arm7 versions, whats the difference?, does the arm7 ver actually run on the arm7?

The ARM7 version runs the DLDI driver code on arm7 instead of arm9 to work around compatibility issues with certain flashcards. Also, DSi/3DS SD access only works on arm7, which is why the DSi/3DS builds only have arm7 support.

 

[fantasma_do_cu_cagado]

Other questions have already been answered, so I'll answer this one:

The ARM7 version runs the DLDI driver code on arm7 instead of arm9 to work around compatibility issues with certain flashcards. Also, DSi/3DS SD access only works on arm7, which is why the DSi/3DS builds only have arm7 support.

Ok, so the game itself is still running on the arm9 (DS mode) with gbarunner as the compatibility layer, while the arm7 just handles DLDI/SD , correct?

And actual native GBA is 100% impossible despite having the arm7, bc the DSi is missing too many other GBA components, would this be a correct conclusion?

 

[RocketRobz]

Ok, so the game itself is still running on the arm9 (DS mode) with gbarunner as the compatibility layer, while the arm7 just handles DLDI/SD , correct?

Yes.

And actual native GBA is 100% impossible despite having the arm7, bc the DSi is missing too many other GBA components, would this be a correct conclusion?

Pretty much. It even lacks the feature to switch into GBA mode.

 

[fantasma_do_cu_cagado]

Thanks!

 

[epicmartin7]

Out of curiosity, does Nintendo's GBA compatibility solution on the 3DS work the same way?

 

[ghjfdtg]

GBA mode on 3DS is fully native. They added back all the hardware necessary for games to run accurately (but this hardware is still not accessible from DSi mode). There is no software emulation involved.