All known games write $02 to $5000, so that when one dumps these cartridges without writing to $5000, defaulting to $00, these dumps cannot be run as TKROM. Dumping as TKROM after having written $02 to $5000 makes the dumps work as mapper 4. Later re-releases of these games that use a simple TKROM-compatible board likewise have the banks arranged matching the $5000=$02 bank order. Games with only 128 KiB of PRG ROM will repeat exactly once within a 256 KiB address space when $5000=$02, with other $5000 values, the repetition pattern is more complex. These are the scrambling patterns, with the PRG bank numbers chosen to reflect the assumption that $5000=$02 is the true ROM content:
Code: Select all
5000=00 5000=01 5000=02* 5000=03
PRG bank 08 PRG bank 10 PRG bank 02 PRG bank 04 (PRG A14)
PRG bank 10 PRG bank 08 PRG bank 04 PRG bank 02 (PRG A15)
PRG bank 04 PRG bank 02 PRG bank 08 PRG bank 10 (PRG A16)
PRG bank 02 PRG bank 04 PRG bank 10 PRG bank 08 (PRG A17)
I am a bit unsure how such games should be stored in .NES format. Currently, mapper 249 ROMs are stored as the banks appear with $5000=$00, and emulators only emulate the $5000=$02 functionality. This also implies that games with only 128 KiB PRG ROM must be stored in overdumped form, which I find extremely undesirable. I also doubt that this is how they are physically stored in the ROM chip/blob; they are much more likely to be stored in $5000=02 bank order. That would make them runnable simply as mapper 4, which is why nes20db considers those "mapper 4 hacks", losing the information that these games boot with $5000=$00, meaning with address line scrambling enabled. Mapper 249 cannot describe that either however, since mapper 249 as already emulated assumes scrambled and possibly overdumped bank order. The following games are affected (and possibly more that I have not checked):
- 三十六計 - The Thirty-Six Tricks
- 夺宝小英豪꞉ 光明與黑暗傳説 (Duóbǎo Xiǎoyīngháo ꞉ Guāngmíng yǔ Hēi'àn Chuánshuō)
- 封神榜 - Myth Struggle
- 楚留香꞉ 香帥傳奇之血海飘零 (Chǔliúxiāng꞉ xiāngshuài chuánqí zhī xuè hǎi piāolíng)
- 水滸傳 - Marsh Outlaws
- 魔法门之英雄无敌 (Mófǎmén zhī yīngxióng wúdí)
- 基督山恩仇记 - Le Comte de Monte Cristo
- 戰斧 - Golden Axe
- 新包青天 II (武鬥篇) - Super Justice King