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DS development > Possible CPU Upgrade through GBA Slot

#34244 - NOX_Kerbanker - Sun Jan 16, 2005 5:42 am

Being that it is possible to load code through the GBA cart couldnt it be possible to add co-processor like capabilities to a standard GBA cart to add more detail and speed to games...

Nintendo prooved it could add additional CPU support through a cartridge ( ie. Starfox SNES )...

Perhaps a NDS-FX chip is on the way......

#34245 - techtech - Sun Jan 16, 2005 5:59 am

That's somewhat unlikely, older console's cartridges (NES in particular)
exposed more buses to the cart (PPU addr/data, CPU addr/data, Extension
port, extra sound (japan only)).

Newer carts (N64, GBC/A) (as far as I know) are essentially just a case
for a storage chip.

Although it's unlikely to be able to directly influence the graphics from
another chip... another chip could be doing extra 3d calculations... is still
unlikely.

#34246 - Darkain - Sun Jan 16, 2005 8:43 am

A) there are already 2 CPUs in the DS. that should be plenty for now
B) in the case of the Super FX chip, AFAIK it disables the SNES CPU while that chip is processing data. they dont both function at the same time... but on the DS, we have the ARM7 and ARM9 running at the same time.
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#34247 - ravuya - Sun Jan 16, 2005 9:28 am

In theory, yeah, it would work. In practice, I'm not sure if the bus on the GBA slot would be efficient enough for this sort of thing.

It wasn't just Nintendo that used custom coprocessors in their cartridges; I've played some C64 games and don't forget the Virtua Racer "SVC" chip.
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#34252 - abigsmurf - Sun Jan 16, 2005 3:20 pm

The play-yan contains a specific mpeg 4 decoder chip which is why it shortens the GBA SP's battery life

#34262 - tepples - Sun Jan 16, 2005 7:58 pm

techtech wrote:
older console's cartridges (NES in particular)
exposed more buses to the cart (PPU addr/data, CPU addr/data, Extension
port, extra sound (japan only)).

Newer carts (N64, GBC/A) (as far as I know) are essentially just a case
for a storage chip.

There are two storage chips in most GBA carts: one for the game program and one for persistent state ("savegame"). In theory, it'd be possible to put ROM, EEPROM, and flash in one GBA cart, at banks 0x08, 0x0D, and 0x0E. I see no reason why any memory-mapped device couldn't be stuffed in a GBA cart. The only thing that having two buses saves is a bit of decoding logic in the ASIC.

And the Super FX didn't disable the Super NES's 65c816 CPU entirely; it disabled only the ROM, and the 65c816 was free to access code and data within RAM.
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#34264 - EaDS Milliways - Sun Jan 16, 2005 8:21 pm

tepples wrote:
techtech wrote:
older console's cartridges (NES in particular)
exposed more buses to the cart (PPU addr/data, CPU addr/data, Extension
port, extra sound (japan only)).

Newer carts (N64, GBC/A) (as far as I know) are essentially just a case
for a storage chip.

There are two storage chips in most GBA carts: one for the game program and one for persistent state ("savegame"). In theory, it'd be possible to put ROM, EEPROM, and flash in one GBA cart, at banks 0x08, 0x0D, and 0x0E. I see no reason why any memory-mapped device couldn't be stuffed in a GBA cart. The only thing that having two buses saves is a bit of decoding logic in the ASIC.

And the Super FX didn't disable the Super NES's 65c816 CPU entirely; it disabled only the ROM, and the 65c816 was free to access code and data within RAM.


Very interesting and what I felt to be one way to "optionize" the DS in the event of extremely strong sales for the PSP (much like when video seems to be a sticking point, Nintendo announces a video player).

#34268 - techtech - Sun Jan 16, 2005 9:17 pm

Quote:
There are two storage chips in most GBA carts: one for the game program and one for persistent state ("savegame"). In theory, it'd be possible to put ROM, EEPROM, and flash in one GBA cart, at banks 0x08, 0x0D, and 0x0E. I see no reason why any memory-mapped device couldn't be stuffed in a GBA cart. The only thing that having two buses saves is a bit of decoding logic in the ASIC.


Silly me, memory-mapping a device in the GBA slot didn't occur to me.
I took the question as a more direct affect on the graphics (sorta like MMC5).

You are, of course, correct :). I'll be quiet now.

#34353 - metis - Tue Jan 18, 2005 2:14 pm

A similair device was made a few years ago for the MSX system.
The MSX uses a Z80 CPU, the add-on has a 32-bit Z380 CPU. Communication was possible via a small bi-port 1 kB memory.

Links:
Creator of the card (in Spanish)
Overview
User's manual