According to the docs i'm looking at this is CNROM with VROM disable. I'm wondering, is this a "made-up" mapper? I'll use Mighty Bomb Jack as an example. It uses a CNROM board which appears to be no different than any other CNROM board. It has a 16KB CHR ROM, but the first 8KB is dummy data. Setting it's mapper to 185 instead of 3, allows you to erase the unused block. Is that why this mapper was created, to save space? or does it actually serve a purpose besides that?
Here is the doc reference:
Here is the doc reference:
Code:
Mapper 185: VROM-disable
Appears to be used for CNROM games with only one (used) 8K VROM bank, however, VROM appears to be bigger than 8K, the games verify the the presence of the unused (empty) VROM banks on startup, and get caught in an endless loop if they do not exist.
8000h-FFFFh (De-)select VROM bank
Values used to switch VROM on/off are:
Off On Title
F0h 0Fh Bird Week
00h 33h B-Wings
00h 11h Mighty Bomb Jack
20h 22h Sansuu 1 Nen - Keisan Game
20h 22h Sansuu 2 Nen - Keisan Game
00h FFh Sansuu 3 Nen - Keisan Game
13h 21h Spy vs Spy
Above games are working when mapping an empty VROM bank (FFh-filled) either when (X)=13h, or when (X AND 0Fh)=0.
Appears to be used for CNROM games with only one (used) 8K VROM bank, however, VROM appears to be bigger than 8K, the games verify the the presence of the unused (empty) VROM banks on startup, and get caught in an endless loop if they do not exist.
8000h-FFFFh (De-)select VROM bank
Values used to switch VROM on/off are:
Off On Title
F0h 0Fh Bird Week
00h 33h B-Wings
00h 11h Mighty Bomb Jack
20h 22h Sansuu 1 Nen - Keisan Game
20h 22h Sansuu 2 Nen - Keisan Game
00h FFh Sansuu 3 Nen - Keisan Game
13h 21h Spy vs Spy
Above games are working when mapping an empty VROM bank (FFh-filled) either when (X)=13h, or when (X AND 0Fh)=0.