INES Mapper 185

 Here are Disch's original notes:

Mapper 185

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Example Games:

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Spy Vs. Spy (J) Mighty Bomb Jack (J)

Registers:

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I'm unsure whether or not this mapper suffers from bus conflicts. I believe it does! Use extreme caution!

 $8000-FFFF:  [CCCC CCCC]
    CHR Reg

Notes:

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This mapper is retarded. These games only have 8k of CHR, but they seem to attempt to disable CHR by writing a specific value to the CHR Reg, then they VERIFY that garbage is read back, then they swap back to the actual CHR. If they don't get the expected garbage, they lock up.

Perhaps this was some sort of copy protection?

Each game has their own value that enables/disables CHR. Rather than failing to attempt to list all the exact values used here (I don't know what all of them are), I can provide some logic:

if C AND $0F is nonzero, and if C does not equal $13: CHR is enabled otherwise CHR is disabled

When CHR is disabled, it is as if CHR is filled with all $12's