#25674 - enliteneer - Thu Aug 26, 2004 10:02 pm
Is it possible to use a 256MB cartridge (like the ezflash advance ones) to make a game thats that big?? Or is the GBA hardware only setup to address 32MB?
#25675 - gb_feedback - Thu Aug 26, 2004 10:14 pm
GBA limit without bank switching is 32 Mbyte.
That is 256 Mbit.
Cartridges are sold in Mbits because it sounds more.
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#25688 - phonymike - Fri Aug 27, 2004 2:06 am
yeah you can freely access all of the 256mbit (32MB) but if you access the next byte after that it'll roll around to the first byte on the cartridge. To access the next byte on say a 512mbit (64MB) cart, you have to send the correct signals to bankswitch it to wherever you want. sorta like
0x8000000 = 0 on flash cart.
0x9FFFFFF = 32MB later on flash cart
0xA00000 = 0 on flash cart (with waitstate 2?)
----------------------
0x8000000 = 0 on flash cart
after bank switching
0x8000000 = 32mbit later
after bankswitching
0x8000000 = 64mbit later
after bankswitching
0x8000000 = 71mbit later
bankswitching changes what the gba sees to a different area of memory on the flash card. sorta like those old orange 3d things you had when you were a kid, where you insert the round paper disk and see some 3d image. ROM carts can't change what you see, so you're stuck on one image, but a flash cart can bankswitch, like flipping the lever and going to the next image :)
#25689 - dagamer34 - Fri Aug 27, 2004 2:11 am
| phonymike wrote: |
yeah you can freely access all of the 256mbit (32MB) but if you access the next byte after that it'll roll around to the first byte on the cartridge. To access the next byte on say a 512mbit (64MB) cart, you have to send the correct signals to bankswitch it to wherever you want. sorta like
0x8000000 = 0 on flash cart.
0x9FFFFFF = 32MB later on flash cart
0xA00000 = 0 on flash cart (with waitstate 2?)
----------------------
0x8000000 = 0 on flash cart
after bank switching
0x8000000 = 32mbit later
after bankswitching
0x8000000 = 64mbit later
after bankswitching
0x8000000 = 71mbit later
bankswitching changes what the gba sees to a different area of memory on the flash card. sorta like those old orange 3d things you had when you were a kid, where you insert the round paper disk and see some 3d image. ROM carts can't change what you see, so you're stuck on one image, but a flash cart can bankswitch, like flipping the lever and going to the next image :) |
You can have have more than 256Mb on a flash cart however the GBA only sees 256Mb at a time, so no, you can't have a ROM file larger than that.
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#25734 - Miked0801 - Fri Aug 27, 2004 9:40 pm
Without special hardware built into the cart for bank switching ala the GBC.
#25744 - phonymike - Sat Aug 28, 2004 12:12 am
yeah let's say one of those movie encoders for gba was made with this in mind. it could check where the data is being decoded from, and if it's at the end of the 32MB the gba sees, it'd bankswitch the cart to the next 32MB, and read from the beginning of rom and keep on going. it's easilly possible (well supporting several carts would suck a tiny bit) but it just hasn't been implemented yet.
#25824 - ampz - Sun Aug 29, 2004 2:06 am
Hopefully pogoshell will implement it... Would be useful.