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UxROM with 4 MB PRG ROM
http://forums.nesdev.com/viewtopic.php?f=3&t=15884
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Author:  zeroone [ Sun Apr 30, 2017 6:47 pm ]
Post subject:  UxROM with 4 MB PRG ROM

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?

Author:  lidnariq [ Sun Apr 30, 2017 6:52 pm ]
Post subject:  Re: UxROM with 4 MB PRG ROM

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.

Author:  zeroone [ Sun Apr 30, 2017 7:08 pm ]
Post subject:  Re: UxROM with 4 MB PRG ROM

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.

Author:  tepples [ Sun Apr 30, 2017 8:44 pm ]
Post subject:  Re: UxROM with 4 MB PRG ROM

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).

Author:  lidnariq [ Sun Apr 30, 2017 9:14 pm ]
Post subject:  Re: UxROM with 4 MB PRG ROM

The same things that would make a GBC or NGPC game reach 32mbit+.

Author:  rainwarrior [ Sun Apr 30, 2017 9:30 pm ]
Post subject:  Re: UxROM with 4 MB PRG ROM

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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