UxROM with 4 MB PRG ROM

Discuss emulation of the Nintendo Entertainment System and Famicom.

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zeroone
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UxROM with 4 MB PRG ROM

Post by zeroone »

From the wiki:
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?
lidnariq
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Re: UxROM with 4 MB PRG ROM

Post by lidnariq »

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
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Re: UxROM with 4 MB PRG ROM

Post by zeroone »

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.
tepples
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Re: UxROM with 4 MB PRG ROM

Post by tepples »

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).
lidnariq
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Re: UxROM with 4 MB PRG ROM

Post by lidnariq »

The same things that would make a GBC or NGPC game reach 32mbit+.
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rainwarrior
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Re: UxROM with 4 MB PRG ROM

Post by rainwarrior »

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.ph ... cts_id=143
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