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zeroone
 Post subject: UxROM with 4 MB PRG ROM
PostPosted: Sun Apr 30, 2017 6:47 pm 
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From the wiki:

Quote:
Emulator implementations of iNES mapper 2 treat this as a full 8-bit bank select register, without bus conflicts. This allows the mapper to be used for similar boards that are compatible.
To make use of all 8-bits for a 4 MB PRG ROM, an NES 2.0 header must be used (iNES can only effectively go to 2 MB).


Why is iNES limited to 2 MB? If emulators treat the bank select register as a full 8-bit register, how is that affected by the header type?
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lidnariq
PostPosted: Sun Apr 30, 2017 6:52 pm 
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iNES (as opposed to NES2.0) cannot encode a 4 MiB PRG ROM, because 255×16 = 4080 KiB, and UxROM as encapsulated in mapper 2 is only well-defined when a power of two in size.
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zeroone
PostPosted: Sun Apr 30, 2017 7:08 pm 
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lidnariq wrote:
iNES (as opposed to NES2.0) cannot encode a 4 MiB PRG ROM, because 255×16 = 4080 KiB, and UxROM as encapsulated in mapper 2 is only well-defined when a power of two in size.


I forgot about the header size limitation. Thanks.
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tepples
PostPosted: Sun Apr 30, 2017 8:44 pm 
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I'm curious about what would need 32 Mbit on the NES, other than a multicart. That's over five times as big as the largest licensed NES game (Kirby's Adventure, 6 Mbit) and four times as big as the largest licensed Famicom game (Metal Slader Glory, 8 Mbit).
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lidnariq
PostPosted: Sun Apr 30, 2017 9:14 pm 
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The same things that would make a GBC or NGPC game reach 32mbit+.
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rainwarrior
PostPosted: Sun Apr 30, 2017 9:30 pm 
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tepples wrote:
I'm curious about what would need 32 Mbit on the NES, other than a multicart. That's over five times as big as the largest licensed NES game (Kirby's Adventure, 6 Mbit) and four times as big as the largest licensed Famicom game (Metal Slader Glory, 8 Mbit).

This recently made music ROM is 64MB:
http://www.retrousb.com/product_info.php?cPath=36&products_id=143
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