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DS development > GBA BIOS on DS still has client roots

#30035 - bcforn64 - Sat Nov 27, 2004 9:57 pm

I was thinking and in the GBA there is a feature where while the GBA is loading if you hold down Start+Select+L Trigger+R Trigger the system becomes in a client state and waits for a Server GBA to upload software to it. Much as if there is no cart in the system. Well, if you do this on the DS while a GBA game boots you get the same exact result. This leads me to conclude that the GBA bios in the DS can't be that much different from a GBA bios on a real GBA, I don't thing it was modified that much.

My battery in my multimeter died so I can't test this on my GBA at the moment, but I believe the link port on the GBA is wired directly to the ARM7. If it is then it may be possible to solder a link port to the DS's ARM7. Of coarse the speed on the ARM7 is doubled so that would throw the bus timings off,but it shouldn't if the ARM7 goes at half speed in GBA mode.

More on this later when I get off work, I think this may have a place in DS hacking besides being able to play multiplayer in GBA games again.

#30037 - PhoenixSoft - Sat Nov 27, 2004 10:14 pm

Are you talking about forcing the GBA into multiboot mode? Because to do that you only have to hold down Start and Select.

#30041 - bcforn64 - Sat Nov 27, 2004 10:52 pm

yes I am, sweet I thought oyu had to hold L Trigger and R Trigger too.

#30047 - tepples - Sat Nov 27, 2004 11:08 pm

bcforn64 wrote:
I believe the link port on the GBA is wired directly to the ARM7. If it is then it may be possible to solder a link port to the DS's ARM7. Of coarse the speed on the ARM7 is doubled so that would throw the bus timings off,but it shouldn't if the ARM7 goes at half speed in GBA mode.

Unless the ARM7 in the DS doesn't bring the link port pins out to the package, leaving them pulled up to Vcc within the package.
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