Talk:Programming UNROM

NES 2.0 advocacy

Converting a ROM from original iNES to NES 2.0 isn't strictly necessary unless the mapper is ≥ 256 or the iNES header is ambiguous. For example:

• Several VRC mappers are ambiguous as to which low CPU address lines are connected to the mapper's port select.
• Mapper 1 is ambiguous between SIROM (PRG A14 from MMC1 output) and other SxROM boards using 32K PRG (PRG A14 from CPU A14).
• Mappers 1, 4, and 5 are ambiguous among PRG RAM sizes. For example, SNROM vs. SOROM, MMC3 vs. MMC6.
• A few games (notably Low G Man) require the PRG RAM to be absent.

What's ambiguous about mappers 2 (UxROM), 3 (CNROM), and 7 (AOROM), other than whether or not the ROM has a positive chip enable to avoid bus conflicts? --Tepples (talk) 22:19, 26 February 2013 (MST)

Two things-

1. the comment about PRG-RAM: due to iNES's shortcomings one can't distinguish between 0="no ram" and 0="unspecified ram"; and
2. the entire point behind NES2.0's backwards compatibility is the encouragement of its adoption without infringing on non-NES2.0-aware emulators. Creating mindshare makes it possible to say that it really is a solution.—Lidnariq (talk) 01:50, 27 February 2013 (MST)