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PostPosted: Tue Feb 24, 2015 4:32 pm 
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Joined: Mon Feb 23, 2015 8:05 pm
Posts: 25
lidnariq wrote:
This is really straightforward hardware to add. It's a 74'138 and a latch such as a (74'74 or 74'161) on top of a board already containing an MMC3.

Wire the 74'138 to detect writes to $41xx by connecting:
R/W to /G1a
A13 to /G1b
M2 to G2
/ROMSEL to A
A8 to B
A14 to C
Then
74'138 /Y7 to latch CLK
CPU D2 to latch data in
latch data out to CHR A18.


wow, thanks... I didn't expect this. I'll still have to check if the rom depends on the other mappers. But this information might make a repro possible again.


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PostPosted: Tue Aug 06, 2019 2:49 am 
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Joined: Mon Apr 24, 2017 10:23 pm
Posts: 7
lidnariq wrote:
This is really straightforward hardware to add. It's a 74'138 and a latch such as a (74'74 or 74'161) on top of a board already containing an MMC3.


Seems it's not so simple. Trying to make repro of AV Mei Shao Nv Zhan Shi (Unl)
Attachment:
20190612_215858.jpg
20190612_215858.jpg [ 512.46 KiB | Viewed 1020 times ]


If mmc3 completely ignore writing to $41xx then this game should work on mapper 04 (just with broken graphics).
Probably 116 mapper do something with mmc3 registers on writing to $41xx because game behaves wrong (on character selection screen and during fight I have freeze and garbled graphics).

For easier reproduction we can change code and move control register for CHR to $6000, because no WRAM in this game and we can use signals from mmc3 instead of 74'138 (like in mapper 189).
If only we can make the rest code work on mapper 4.


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PostPosted: Tue Aug 06, 2019 1:28 pm 
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Joined: Sun Apr 13, 2008 11:12 am
Posts: 8533
Location: Seattle
If it crashes like that, odds are good that it's using MMC1 mode in order to change what would be MMC3's fixed bank, and so I fear an MMC3 mapper hack would be impossible.


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